Stress on Frontline Employees from Customer Aggression in the Restaurant Industry: The Moderating Effect of Empowerment

In service industries such as restaurants, abusive customer (jay-customer) behaviors may evoke emotional exhaustion and burnout in frontline employees, threatening job satisfaction as well as sustainable management in the hospitality industry. Therefore, there is a need to identify whether (and to what degree) such customer behaviors stress frontline employees enough to affect their mental health, which may lead to employee turnover. To understand jay-customer behaviors in a restaurant setting, this study investigated the factors of jay-customer behaviors that induce job stress and decrease job satisfaction. Additionally, the moderating effect of empowerment was tested to see whether employee empowerment decreases the stress caused by jay-customer behaviors. Data collected from 302 restaurant employees from several cities in South Korea were analyzed using exploratory factor analysis and structural equation modeling. The study results demonstrate that three types of jay-customer behaviors (verbal abuse, physical abuse, and sexual harassment) are directly related to frontline employees’ job stress, which in turn, reduces job satisfaction. A moderating effect of empowerment on the relationship between verbal abuse and job stress is found. The results of this study suggest a conceptual model for understanding the process in which jay-customers negatively influence the frontline employees, threatening employee well-being, and they provide valuable implications for the restaurant industry, which can help develop strategies to improve employee welfare and provide better customer management.


Introduction
When it comes to organizational sustainability, one can only imagine the economic and strategic aspects of organizational initiatives or goals that are set in order to maximize profit. However, organizational sustainability, entailing the concept of sustainable development at the organizational level, requires an organization to think beyond profit [1,2]. While economic profitability is essential for firms that want to attain long-term success, organizational sustainability emphasizes that firms not only think beyond their shareholders but also that they are managed in accordance with the interests of all their stakeholders [2][3][4]. This is because, according to stakeholder theory [5,6], all stakeholders (including employees) provide resources to an organization, and all of them contribute to the wealth of the organization [7,8].
In the food service industry, where the human element is heavily involved in the course of service delivery, frontline employees are among the internal stakeholders who are considered crucial evaluative factors in the organizational performance impacting a firm's profitability in the long term [9]. Considering sustainable development at the organizational level to be the process of meeting the needs of the firm's present and future stakeholders [2,10], one way the restaurant industry attains organizational sustainability may be through paying attention to the needs of employees, thereby achieving effective performance in the present, and not damaging future achievement [11,12]. Indeed, prior research has found that social and economic goals and initiatives that airline industry leaders established and adopted for the sustainability of their operations included employee health, safety, and well-being, and employee involvement and empowerment [13].
The customer-first strategy is a well-known maxim widely accepted by individuals, businesses, and society. It is a customer-centric mindset that serves as the business strategy for service employees in order to create delightful customer experiences by putting their customers at the center of every service encounter [14]. Conversely, the prevalent phenomenon of the customer-first strategy gives some customers the illusion that employees come second [15,16], which engenders difficulties in managing restaurants sustainably (e.g., creating employee stress, burnout, or dissatisfaction). In order to promote a sustainable hospitality industry, it is crucial to handle the ethical issues in managing employees in the workplace. Therefore, the current study pays attention to frontline service employees in the restaurant industry, who often suffer from customer aggression in service encounters, and it attempts to provide meaningful insight into ways to improve the workplace and ensure sustainability.
Jay-customers are individuals who act in abusive ways that bring trouble to the company, its staff, and other customers [14]. They may act abnormally [17], be dishonest [14], or take advantage for financial gain [17]. Practitioners emphasize the fact that these behaviors are prevalent in the workplace [17][18][19]. Grandey, Dickter and Sin [18] found that a significant portion of US customer-contact employees suffers from verbal abuse daily, leading to emotional exhaustion or employee burnout. In the hospitality industry, almost half of customer-contact employees were found to have experienced physical abuse from customers, and 38% of them needed medication [17]. Balloch, et al. [20] indicated that most employees feel their organizations do not adequately take care of the emotional impact of customer physical violence against employees. Workplace sexual harassment and abuse occur more frequently and seriously than predicted; they deeply affect employees' physical and mental health and disrupt careers [21]. The restaurant industry is particularly service-oriented, where frontline employees directly face their customers [22]. The blurry line between work and social interaction makes it difficult to regulate harassment in the restaurant industry [23,24], making restaurant employees more vulnerable to jay-customer behaviors [25,26]. Additionally, restaurant culture seems to recognize verbal abuse and harassment as natural factors of a work environment [27]. The negative effects of jay-customer behaviors on restaurant frontline employees are more serious in Asia [22,28] owing to the fact that Confucian values dictate that service employees should endure jay-customer behaviors in the restaurant industry [22]. In response to these facts, the whole of society calls for more attention to empirically understanding the above abusive behaviors [15][16][17].
The effects of jay-customer behaviors have been explored in various hospitality and tourism contexts, such as casinos [29], group package tours [30], and restaurants [22]. Jaycustomer behaviors affect the "organization's employees, merchandise, customers, (and) financial assets" [17], leading to stressful conditions in the work environment [26,31,32]. Liu, Kwan and Chiu [22] revealed that sexual harassment by jay-customers lowers frontline employees' performance by making it difficult for them to maintain display rules in the restaurant industry. Kim, Ro, Hutchinson and Kwun [26] verified that customer incivility and aggression induce job stress among customer-contact employees in the hospitality industry. Such jay-customer behaviors also increase operating costs, threaten corporate interests [33], and influence employee turnover in the tourism industry [16]. Even worse, employee job stress caused by jay-customer behaviors diminishes job satisfaction [26], further affecting customer satisfaction with the company [34]. As such, understanding jay-customer behaviors can provide a reference point for reducing employee stress and monitoring job satisfaction [18,26].
While prior studies have focused on the influences of jay-customer behaviors [22,26], they neglected to consider employee perceptions of power, which can mitigate the negative effects of jay-customer behaviors on frontline employees in the restaurant industry. Kanter's theory of structural power in organizations indicates that employee empowerment can alleviate the stress that arises when employees encounter difficulties at work [35,36]. Since frontline employees are required to quickly meet customer needs and resolve customers' problems [22,37], empowerment enables employees to better control incidents and issues that occur in workplaces [38].
In this regard, this study proposes a conceptual model to understand jay-customer behaviors that may significantly evoke frontline employees' stress and burnout in the workplace and threaten their job satisfaction in the restaurant industry. Specifically, this study aims to answer three main questions: (1) What jay-customer behaviors determine frontline employees' job stress? (2) Does job stress caused by jay-customer behaviors influence frontline employees' job satisfaction? (3) Does employee empowerment moderate the relationship between jay-customer behaviors and job stress? Interpreting jay-customer behaviors can be effective business management, reducing losses incurred in various service industries [14,33,34]. In this way, the results of this study contribute to the literature by providing a theoretical understanding of the process through which jay-customers affect frontline employees in a service encounter. In addition, companies in customercentric industries, including the restaurant industry, can benefit from the study results through a better understanding of the harmful effects of jay-customer behaviors and the importance of promoting service employees' physical and mental wellness in the workplace. This ultimately helps them promote their own effective employee-development and customer-management strategies that contribute to employee welfare and provide competitive advantages in the sustainable hospitality market.
Various factors affect jay-customer behaviors [29,43,49]. Fullerton and Punj [43] explained that jay-customer behaviors are derived from the interaction of market influences with personal characteristics and tendencies. For example, pursuing irritation could cause vandalism [50]. Huefner and Hunt [49] mentioned that customers' perceived injustices and dissatisfaction lead to jay-customer behaviors like vandalism, trashing, stealing, negative comments spread by word of mouth, and personal attacks. In the casino industry, Fong, So and Law [29] discovered that conflicts between employees and customers are a common cause of verbal abuse. As such, the causes of jay-customer behaviors are complex and diverse [14,29,43,49].
Combined with the research background, this study focuses on the following three aspects: verbal abuse, physical abuse, and sexual harassment. Verbal abuse can be defined as customers using impolite language to humiliate employees, treating employees with disrespectful attitudes, or yelling at employees. Harris and Reynolds [17] found that verbal abuse is the most common jay-customer behavior occurring in the hospitality industry. As a form of workplace violence, verbal abuse committed by customers deeply hurts employees' feelings [31], causing devastating emotional damage [54]. In addition, customer verbal abuse negatively impacts employees by decreasing their morale [31,55], leaving employees exhausted and disengaged [56], decreasing job satisfaction [25], and even increasing employee turnover [25]. Physical abuse means that customers physically harm an employee, act aggressively/violently toward an employee, or physically destroy a restaurant's property/equipment. Physical abuse causes varying degrees of injury to employees [17], ranging from a slight push to all-out attacks causing injury [32]. Scholars found that workers who experienced physical abuse might be reluctant to report it to police because they worry about losing their job or facing retribution [29,57]. Sexual harassment includes deliberate sexual touching, making sexual comments, or physical harassment. Harris and Reynolds [17] found that sexual harassment also happens to male workers. It seriously threatens employees' job performance [22] and well-being [58]. In hospitality workplaces, including restaurants, the boundaries between work and social interaction are vague, which makes it difficult for companies to control sexual harassment by customers [23,24]. Traditional Confucian values particularly prevalent in Asian culture expect employees to tolerate the emotional impact of this behavior [22,23].

Job Stress
Job stress can be defined as negative emotional responses that occur when work situations exhaust employees, and when work-related factors put pressure on them. Job stress can change employees' physical and psychological states and cause them to deviate from normal functions [59]. Employees experience particular stress awareness in response to what happens in the work environment [60]. Stress awareness includes "job-related tension, anxiety, frustration, worry, emotional exhaustion, and distress" [61]. Job stress is the result of complex interactions between people and the work environment [59]. Especially in a service-oriented environment, employees need to face customers directly [22], are required to serve customers with friendly, respectful, and enthusiastic attitudes [62], and are therefore likely to experience greater stress [20]. Zohar [63] mentioned that frontline employees and managers in the hotel industry are subject to high levels of conflict, ambiguity, work overload, and limited decision latitude. Thus, the diverse and complex requirements that frontline employees are expected to follow in the workplace may increase frontline employees' stress on the job [19,22,26,28].
Jay-customer behaviors are the most significant cause of job stress in the restaurant industry [22,26,27]. Specifically, verbal abuse that may be inevitable for frontline employees when it occurs [18,64] upsets employees [31]. Johns and Menzel [19] revealed that violence can cause personal injury and brings social disruption, resulting in personnel turnover, absenteeism, and job stress in the restaurant industry. A study of the social service workforce by Balloch, Pahl and McLean [20] revealed that employees who suffer physical abuse in the workplace feel anxious or depressed to varying degrees. Liu, Kwan and Chiu [22] suggested that sexual harassment is considered a source of stress for frontline employees in the restaurant industry. In summary, this study posits that verbal abuse, physical abuse, and sexual harassment committed by jay-customers are likely to increase the job stress perceived by frontline employees in the restaurant industry.

Job Satisfaction
Job satisfaction can be defined as the extent to which an employee is content with and loves his/her job and the working environment [65,66]. Job satisfaction reflects a pleasant emotional state that an employee's work or work experiences bring to them [67]. This positive emotional state includes a positive attitude toward the workplace [68] and customers [69], and personal feelings that reflect the employee's contentment with his/her job [61].
In the hospitality industry, job satisfaction, to a large extent, promotes employees' respect for customers [69] and their desire to provide better quality service, which ultimately creates pleasant experiences for customers [70] and increases customer satisfaction [66]. Therefore, companies tend to place a high priority on job satisfaction in order to enhance competitiveness in service markets [69].
Previous studies established that job stress caused by jay-customer behaviors negatively influences job satisfaction [26,27,71,72]. Kim, Ro, Hutchinson and Kwun [26] found that job stress generated from jay-customer behaviors reduces job satisfaction of guestcontact employees in the hospitality industry. Using data collected from non-supervisory employees in the restaurant industry, Kim and Jogaratnam [72] revealed that job stress has a negative impact on job satisfaction. O'Neill and Davis [71] argued that job stress decreases job satisfaction and increases hotel employee turnover. Thus, the current study posits that job stress perceived by restaurant frontline employees is likely to decrease their job satisfaction, as expressed in H4: Hypothesis 4 (H4). Frontline employees' job stress negatively influences job satisfaction.

The Moderating Role of Empowerment
Empowerment refers to the authority employees have to independently correct and address issues related to jay-customer behaviors. According to Kanter's theory of structural power in organizations [35,36], empowered individuals have access to resources, knowledge, support, and chances that give them control over the issues that occur in workplaces. Empowerment links individual strengths, help-awareness, and proactive behaviors with social policies and social reform [73], thereby enhancing employees' ability to cope with threats [74] such as aggressive customer behaviors [75].
Employees' job stress caused by jay-customer behaviors may be relieved through creating a work environment that gives employees control, autonomy, and decision-making opportunities in the workplace [75][76][77]. Employee empowerment strengthens employee mobility, concentration, resiliency, or flexibility to respond to work emergencies [78]. In the process of empowerment, employees believe they have the ability to influence work results, to accomplish organizational goals, and to improve the work environment [74]. Therefore, employees may be more engaged and motivated at work [79]. Ben-Zur and Yagil [75] indicated that empowering service personnel can be an effective method to relieve burnout resulting from customer abuse. Hence, this study proposes that empowerment is likely to moderate the effect of jay-customer behaviors on job stress as follows: Hypothesis 5 (H5). Empowerment moderates the impact of a customer's verbal abuse on frontline employees' job stress in such a way that the impact on job stress of a customer's verbal abuse is weaker in the group of more empowered service employees than in the group of less empowered service employees. Hypothesis 6 (H6). Empowerment moderates the impact of a customer's physical abuse on frontline employees' job stress in such a way that the impact on job stress of a customer's physical abuse is weaker in the group of more empowered service employees than in the group of less empowered service employees.
Hypothesis 7 (H7). Empowerment moderates the impact of a customer's sexual harassment on frontline employees' job stress in such a way that the impact on job stress of a customer's sexual harassment is weaker in the group of more empowered service employees than in the group of less empowered service employees.
Based on the aforementioned hypotheses, this study proposes the research model shown in Figure 1.

Measures
To measure each construct in the current research, scales utilized in the literature were further developed. Specifically, to measure jay-customers' behaviors, scales were developed based on initial items generated in previous studies [17,80,81]. To fit items to the restaurant industry, experts in the restaurant industry (two professors, three practitioners, and three graduate students) reviewed the initial items and judged whether items should be added or deleted and whether measurement items were suitable for frontline restaurant employees. After developing the items, a pre-test was conducted, and 51 responses were collected from graduate students who had experienced jay-customer behaviors while working as any kind of frontline worker in any restaurant, regardless of the position. The items of jay-customer behavior were measured on a five-point Likert scale where, in response to the question, "How often do you encounter or experience the following types of customer behavior?" 1 = never to 5 = all the time. Through the pre-test, sub-dimensions of jay-customer behavior were extracted using exploratory factor analysis (EFA). The EFA results revealed a Kaiser-Meyer-Olkin (KMO) measure of 0.649, and Bartlett's sphericity test results showed that the data were well-suited to conducting factor analysis (χ 2 = 177.901, df = 36, p < 0.001). Four of the 17 items were discarded because of cross-loading or an indication of low factor loadings (below 0.5) because factor loadings for practical significance are values greater than ±0.50, even though factor loadings of ±0.30 to ±0.40 are acceptable as cut-off values [82]. Accordingly, jay-customer behavior was categorized into three sub-dimensions: verbal abuse, physical abuse, and sexual harassment. Verbal abuse consisted of three items, and indicated an eigenvalue of 2.128, with explained variance at 23.645%; physical abuse consisted of three items and indicated an eigenvalue of 2.169, with explained variance at 24.103%; and sexual harassment consisted of three items and indicated an eigenvalue of 1.980, with explained variance at 22.005%. The total explained variance was 69,754%. In addition, reliability was also confirmed by indicating that, for all dimensions, Cronbach α values were greater than the 0.7 cut-off value [82].
Job stress was operationalized with three items adapted from Kim, Ro, Hutchinson and Kwun [26]. Job satisfaction was assessed with three items adapted from Rich [65] and Homburg and Stock [66]. Empowerment was evaluated with four items adapted from Gong, et al. [83]. The items were measured on a five-point Likert scale where 1 = strongly disagree to 5 = strongly agree.

Data Collection and Sample
To test the hypotheses in this research, an onsite survey was conducted by targeting frontline employees currently working in restaurants. Selection criteria were adopted to target frontline restaurant employees who experienced Jay-customer behaviors. To obtain representative research samples, restaurants in several cities in South Korea, such as Seoul, Busan, or Suwon, were selected for distributing the questionnaire. An anonymous, selfadministered survey was conducted from February to April 2018. For access to restaurants, we first contacted restaurant owners and managers who had contacted and maintained good relationships with other restaurant owners and managers by using snowballing sampling method. We obtained approval from participating restaurant owners and managers, and they introduced a number of frontline service employees to a survey team. With their help, we visited the restaurants and invited frontline restaurant employees to participate. After confirming the employees were frontline service providers in their restaurants, the survey team explained the purpose of the research and asked them to participate in a survey. Then, we distributed a questionnaire only to frontline employees who expressed willingness to help us with our request. They were asked to complete the questionnaire in a place in which there were no supervisors, assuring the respondents' privacy as well as the data's confidentiality.
The questionnaire provided two screening questions in order to select suitable participants. The first question was, "Are you serving customers in the restaurant as a frontline employee?" (Frontline employee refers to workers who provide services face-to-face with customers, including waiters/waitresses for restaurant hall service or restaurant counters.) The second question was, "Have you ever encountered jay-customer behaviors when serving customers in the restaurant? (Jay-customer behavior refers to dysfunctional behavior of customers who may intentionally or deliberately behave improperly and disrupt service with verbal abuse, physical abuse, and/or sexual harassment, which negatively affects the company, employees, or other customers in the restaurant.) If participants chose "No" to either screening question, the survey was terminated. Of the 380 questionnaires distributed, 319 responses were returned, representing a response rate of 83.9%. After excluding invalid 17 responses (e.g., outliers/missing values) from the collected data, a total of 302 responses were used for further analysis. Table 1 summarizes the profiles of the respondents.
As presented in Table 2, the results showed the standardized factor loading for each item was over 0.50, ranging from 0.507 to 0.929, and the average variance extracted (AVE) for each construct was greater than 0.50, ranging from 0.521 to 0.688. Therefore, convergent validity was confirmed [85]. Cronbach α values were over 0.7, thus indicating all items and constructs were reliable. To estimate discriminant validity, the squared correlation for each construct pairwise was compared with corresponding AVE values. As shown in Table 3, all AVE values were greater than the squared correlations, indicating all factors differed from one another. Thus, discriminant validity was confirmed. Composite reliability of each construct was greater than 0.7, ranging from 0.830 to 0.936 as presented in Table 3, showing each construct was consistent internally. Table 2. Confirmatory factor analysis (CFA) items and loadings.

Items
Loading
The path coefficients of the causal relationships among constructs are in Table 4. The results indicate that three sub-dimensions of jay-customer behaviors are predictors enhancing frontline employees' job stress. Specifically, a customer's verbal abuse had a significant effect on frontline employees' job stress (β = 0.166, p < 0.05; H1 was supported); a customer's physical abuse significantly predicted frontline employees' job stress (β = 0.261, p < 0.05; H2 was supported); and a customer's sexual harassment was significantly related to frontline employees' job stress (β = 0.203, p < 0.05; H3 was supported). Additionally, frontline employees' job stress had a negative impact on job satisfaction (β = −0.452, p < 0.01), indicating H4 was supported.

Moderating Effect of Empowerment
For a moderation test, multi-group analysis was conducted by dividing samples into two groups: more empowered employees (n = 177) and less empowered employees (n = 125). Two sub-groups were separated out according to the median sum of empowerment score. Using a chi-square difference test, an unconstrained model was compared with a constrained model to verify differences between the two groups.
The results of multi-group analysis are illustrated in Table 5. Empowerment significantly moderated the relationship between a customer's verbal abuse and employees' job stress [∆χ 2 (1) = 4.454, p < 0.05]. Therefore, H5a was supported. More specifically, in the group of more empowered frontline employees, a customer's verbal abuse did not have a significant effect on employees' job stress (β = 0.035, p = 0.705), whereas, in the group of less empowered frontline employees, customer verbal abuse significantly affected employees' job stress (β = 0.461, p < 0.05). However, empowerment did not moderate the effect of physical abuse on employees' job stress [∆χ 2 (1) = 0.162, p < 0.05] or the effect of sexual harassment on employees' job stress [∆χ 2 (1) = 1.714, p < 0.05]. Therefore, H5b and H5c were not supported.

Discussion and Implications
In order to promote the sustainable hospitality industry, it is crucial to handle the ethical issues of managing employees in their workplace. This research was aimed at understanding jay-customer behaviors encountered in the restaurant industry from the perspectives of frontline employees and is intended to provide empirical suggestions for responding to jay-customer behaviors. Using data collected from restaurant employees in several South Korean cities, this study explored the research model proposed in order to identify the relationships among jay-customer behaviors, job stress, and job satisfaction, and the moderating role of empowerment on the relationship between jay-customer behaviors and job stress. The results of SEM confirmed the linkage "jay-customer behaviors-job stress-job satisfaction" as proposed in this study; however, the moderating role of empowerment was found to be significant only on the relationship between verbal abuse and job stress. The study findings have several theoretical implications.
First, the results of this study suggest that the multidimensionality of jay-customer behaviors provides deep and broad knowledge contributions to, and confirms the existence of jay-customer behaviors in, the restaurant industry. The results also raise awareness about the seriousness of jay-customer behaviors, and they increase the concern for workplace sustainability in the restaurant industry. Specifically, this study identified three types of jay-customer behaviors that frequently happen to frontline employees in the restaurant industry: verbal abuse (i.e., demeaning or derogatory and condescending remarks; venting of frustrations), physical abuse (i.e., physical damage; disorderly conduct under the influence of alcohol; vandalism/theft), and sexual harassment (i.e., offensive comments; sexual molestation; physical and bodily contact). The study results found that frontline restaurant employees particularly experience verbal abuse the most, followed by sexual harassment and physical abuse. In other words, frontline restaurant employees have had to deal directly with jay-customers who use offensive language, speak impolitely, or verbally and physically harass them in sexually offending ways, and who intentionally damage restaurant property. The results of this study demonstrated that inappropriate customer behaviors are complex and indeed exist in the restaurant industry [17,27,41].
Second, the results of this study highlight the effects of jay-customer behaviors that impose job stress on frontline restaurant employees-specifically, verbal abuse, physical abuse, and sexual harassment. In particular, all three types of jay-customer behaviors were found to influence job stress. Among them, physical abuse was found to have the strongest effect on job stress, followed by sexual harassment and verbal abuse. Overall, because direct aggression is committed by restaurant customers, jay-customer behaviors are likely to increase job stress (i.e., workplace stress, exhaustion, and burnout) as perceived by frontline employees, which confirmed the findings of previous studies [22,26]. Moreover, the study results showed that job stress strongly relates to job satisfaction, which also supports findings in previous research [26,66,71,72].
Third, empowerment was found to moderate the relationship between jay-customer behaviors and job stress. The study findings particularly show that the effect of verbal abuse on job stress is significant only among less empowered employees, but is not significant among more empowered employees. Such results confirm that, while verbal abuse by jay-customers does not affect frontline restaurant employees' job stress if they are highly empowered, it positively increases job stress if they are less empowered. Frontline employees who have the authority to correct customer-related problems themselves have more control over decision-making opportunities in the workplace. Empowerment may effectively manage workplace stressors caused by the jay-customer behavior of verbal abuse. On the other hand, empowerment was found to be insignificant in moderating the effects of physical abuse and sexual harassment on job stress. Since physical abuse and sexual harassment are severe acts of violence that mostly transcend legal boundaries, frontline employees may not be able to deal with such behaviors by themselves, whether they are highly empowered or not.
The results of this study raise significant concerns for restaurant owners. Boisterous and rude customers frequently appear in restaurants [64] where frontline employees already often work in a stressful environment [27] dealing with unusual work hours and working conditions, and face-to-face interactions with customers [86]. Accordingly, this study provides several recommendations concerning jay-customer behaviors. First, industries should be responsible for minimizing the possibility of inappropriate behaviors [17,87] and must effectively handle jay-customer incidents [47]. To respond to incidents related to jay-customer behaviors, management can collect relevant information from employees who experience these behaviors and can develop solutions based on employee experience. For instance, companies can provide opportunities for psychological treatment and medical care for employees who experience jay-customer behaviors that cause physical and mental stress [59]. Training or educational programs can be provided at the corporate level to help employees cope better with the undesirable situations that occur in the workplace. Second, restaurants can take action to reduce their employees' job stress. Stress management training and employee assistance programs, for example, can help employees decrease and eliminate the effects of stress, such as insecurity and anxiety. Third, employees may not respond to and remain silent on inappropriate customer behaviors toward them because of fear of retaliation (e.g., losing their jobs) [29]. For their part, companies can establish confidential employee management systems to protect sensitive personal employee information so that any jay-customer behaviors do not go unreported.
This study has certain limitations and offers some suggestions for future research. The focus was on the negative impact of jay-customer behaviors on employees while neglecting its potential impact on other customers [26,88]. Future research may explore how jay-customers behaviors influence other customers' perceptions. In addition, the current study did not consider the demographic characteristics of jay-customers. For example, there exists a certain gender difference in such customers [89]. Future studies need to examine the differences in the levels of job stress and job-satisfaction influence by jaycustomer behaviors across demographic subgroups.

Conclusions
Customers' abusive behaviors toward frontline employees in the restaurant industry increase employees' emotional damage and burnout, threatening restaurant employees' physical and mental health, and even employee wellness. Therefore, controlling and preventing jay-customer behaviors and eliminating stressful factors are conducive to reducing stress-induced work situations and creating a healthy work environment, improving the productivity and morale of frontline employees, and increasing job satisfaction in the restaurant industry. In this study, a conceptual model was developed to empirically test how jay-customer behaviors influence frontline employees' job stress and, therefore, decrease job satisfaction, and whether employee empowerment plays a role in reducing the effect of jay-customer behavior on job stress. SEM assessed the research hypotheses using data collected from restaurant employees, and revealed significant relationships between jay-customer behaviors (verbal abuse, physical abuse, and sexual harassment) and job stress, and showed a relationship between job stress and job satisfaction. Empowerment was significant in moderating only the relationship between verbal abuse and job stress. Consequently, this study offers hospitality industries valuable insights into the importance of promoting a holistic sustainable workplace by managing and supporting employee mental health and wellness through understanding the sources of stress, such as jay-customer behaviors.
Author Contributions: Y.B., the first author, wrote and edited the original draft of the manuscript. S.C., the second author, reviewed the literature and revised the manuscript. J.Y., the corresponding author, designed the research model and visualized the statistical results. I.K., the corresponding author, supervised the research project and collected and analyzed the data. The distinctive knowledge and experience of each author equally contributed to developing this research article. All authors have read and agreed to the published version of the manuscript.