A Systematic Review of Experimental Studies Investigating the Effect of Cause-Related Marketing on Consumer Purchase Intention

Cause-related marketing (CRM) is a globally popular marketing technique due to its value to multiple stakeholders such as the companies, the consumers, the non-profit organizations, and the society. The key to successful CRM is the consumer purchasing the cause-related product, and experimental methodology was adopted mostly during this process. Therefore, this paper systematically reviewed the CRM literature that measured consumers’ purchase intentions using the experimental methodology. A systematic literature research was undertaken examining five databases and 68 qualified articles were identified. The results showed that CRM in most qualified studies is manipulated as a tactical marketing program and the products are mainly low-cost and low involvement. Moreover, the CRM is more effective than the ordinary marketing or sales promotion strategy, such as discount and coupons. Furthermore, the specific characteristics of the CRM program (e.g., donation amount, cause type, message framing) have shown positive outcomes but mixed effects are persistent. Recommendations for implementing CRM programs and for future research were discussed.


Introduction
Both corporate social responsibility (CSR) and corporate citizenship theories require the company not only to achieve economic goals but also to contribute to the sustainable development of society [1,2]. Further, consumers in the 21st century are increasingly aware of socially responsibility, have higher CSR expectation and hope to participate in CSR activities [3]. In this context, it is critical for the companies to attract socially responsible consumers and meet their needs while keeping their business profitable and sustainable.
Cause-related marketing (CRM) is a marketing approach that has been proven to be capable of benefitting the company, the consumers, and the society simultaneously. It refers to the process of formulating and implementing marketing activities in which one firm commits to donate a specific amount to a non-profit organization (NPO) or social cause when customers purchase their products [4]. CRM provides multiple benefits to the company, the consumers, NPOs, and society. Benefits for the company include positioning the company and branding differentially [5], increasing sales and market share [6], establishing long-term customer relationships (e.g., customer satisfaction, loyalty and repurchase) [7], and enhancing image and reputation [8,9]. Consumers fulfil their needs not only for product/service but also for goodwill and prestige [10]. NPOs receive more funding, thus helping more people, more often [11]. Causes are also improved or developed [12]. Therefore, the CRM strategy has The selected databases were chosen based on their significant relevance to business and marketing disciplines. The use of * allows for singular or plural word forms to be identified. A total of 1053 were retrieved from 5 databases. Records gathered from databases may vary due to different specializations of different databases and their relation to the search terms. See Table 1 for more details. All downloaded records were collated using Endnote 8.0. As multiple databases may include the same journals, duplicate records had to be removed, reducing the number of unique articles to 525. Next, unqualified records including conference papers, dissertations and book sections were removed. Titles and abstracts were then reviewed and irrelevant articles (not mentioning CRM) were excluded, which reduced the number to 364. Records related to CRM, not in English, reviews and conceptual papers, case studies, qualitative studies using interview and quantitative research using questionnaire or survey were excluded, leaving 130 experimental studies. The studies varied widely in the measurement of how consumers react to the CRM campaign, including consumer perception [31], attitude [32], willingness to pay [33], PI and others. The qualified articles are those that measured PI, which is the immediate determinant of buying behavior [34]. So, the experimental studies not measuring PI were also excluded. A total of 68 qualified articles remained following the exclusion criteria. The review process is summarized in Figure 1.
The following data were extracted and analyzed from the included papers: 1. Study characteristics, including experiment locations, theory used, sample size, etc.

2.
Experiment conditions, including product types, whether the company/brand is fictitious, the social causes, and the donation size. 3.
Experimental variables, including all kinds of independent variables (the determinants of PI, such as brand awareness, company motivation, message framing, etc.), dependent variables (other than PI), any moderators/mediators (if any), as well as the effects on PI.
All data were extracted from the include studies by the lead author and a random 10% of the papers were again extracted by the second author. The final data were then compared and cross-checked to ensure reliability. Discrepancies were minor and were resolved by discussing with the third author. Sustainability 2020, 12, x FOR PEER REVIEW 4 of 22

Study Characteristics
There was a total of 68 qualified articles that researched CRM with experiment and measured consumer PI as the dependent variable. The number of experiments in each article was diverse. Half of the qualified papers conducted one experiment (n = 35), while others conducted more than one experiment (up to five). It is worth noting that the multiple-experiment articles did not necessarily measure PI for every experiment. For example, Chen (2016) [35] conducted five studies but only measured PI in the fifth study. In these cases, we only show the study that measured PI. Therefore, there are 102 experiments in total (see Table 2).

Study Characteristics
There was a total of 68 qualified articles that researched CRM with experiment and measured consumer PI as the dependent variable. The number of experiments in each article was diverse. Half of the qualified papers conducted one experiment (n = 35), while others conducted more than one experiment (up to five). It is worth noting that the multiple-experiment articles did not necessarily measure PI for every experiment. For example, Chen (2016) [35] conducted five studies but only measured PI in the fifth study. In these cases, we only show the study that measured PI. Therefore, there are 102 experiments in total (see Table 2).     Among the 68 qualified papers, nearly half of the studies were conducted in the USA (n = 33), followed by China (n = 9), Italy (n = 4), Germany (n = 4), Canada (n = 3), Australia (n = 2), South Africa (n = 2), and one in UK, Spain, France, Austria, Netherland, New Zealand, South Korea, India, Thailand, Poland and Oman. Overall, most studies were conducted in developed countries (n = 55) and China is the developing country that most interested in CRM research.
Among the 102 experiments/studies, these studies were based on 41 theories from the fields of psychology, sociology, advertising, economics, management, etc. The most used theory was attribution theory (n = 10), followed by elaboration likelihood model (ELM) (n = 9), consistency theory (n = 9), social exchange theory (n = 5), signaling theory (n = 5), information integration theory (n = 4), associative theory (n = 4), cognitive dissonance theory (n = 4), social identity theory (n = 4), perceptual fluency theory (n = 3), and the persuasion knowledge model (PKM) (n = 3). It is also noteworthy that popular behavioral explanatory theories such as social cognitive theory and the theory of planned behavior (TPB) only appeared once. The most used theory was attribution theory (n = 10), which specifies how the social perceiver used information to arrive at causal explanations for events [98]. The second most used theory was ELM and consistency theory, which were both adopted in nine studies. The ELM of persuasion is a dual process theory describing the change of attitude [99]. The consistency theory, which was also named congruency theory [31,72], includes the cue consistency [43,53,67], cognitive consistency [73], and commitment-consistency principle [92].
The social cause was also diverse including health (n = 30), educational (n = 18), food/nutrition (n = 15), environmental (n = 14), humanitarian aid (n = 14), animal (n = 6), sanitation (n = 2) and cultural (n = 1). The health-related cause mainly referred to the medical research of many diseases, such as breast cancer, skin cancer. The humanitarian aid category referred to providing help to those affected by traffic accidents, the victims of disasters, and orphaned children around the world. The congruency between the products and the social cause was high. For example, the company combining the sales of notebook with a children educational program, or the water company donating to the environmental cause.
The number of studies that used a true company (n = 29) as experimental stimuli was slightly more than that of those using a fictitious company (n = 26). There are five studies that used both a true and fictitious company so as to increase the experimental validity. Moreover, eight studies did not indicate the company or brand information. About the donation, most studies used monetary donation (n = 60) and only three studies used nonmonetary donation (i.e., product). Furthermore, there are five studies which did not detail the donation size or type, and just said "make a donation". The monetary donation includes donating a specific amount of cash for per sale (n = 28) and donating a portion of the price (n = 18), sales (n = 13) or profits (n = 4). Both the donation sizes of cash and percentage were diverse, ranging from USD 0.05 to USD 23 and 0.1% to 50%, respectively. Overall, the most used donation size was 5% of sales (n = 8), followed by 5% of price (n = 6), USD 0.05/per sale (n = 5), USD 1/per sale (n = 5). Few donation sizes were larger than those.

Determinants and Effects on PI
The sample of 68 papers included 102 studies that presented a variety of independent variables that may affect PI. Overall, forty-seven percent of studies (n = 48) found positive effects of different variables on PI, while fifty-three percent of studies (n = 54) found mixed, negative or not significant effects.
One of the main independent variables evaluated is the presence or absence of CRM. Five studies showed positive effects of the presence of CRM [37,39,45,81] and only two studies found mixed and not significant effects, showing strong evidence of the effect of CRM on PI. Additionally, donation related variables that may affect PI were evaluated. Eleven studies assessed the effect of the donation amount, finding positive results in three cases [56,84], mixed results in five cases and negative in one case. Similarly, seven studies examined donation type (cash or product) finding positive results in two cases [55] while five found mixed, negative or not significant effects. Likewise, four studies evaluated donation framing (percentage of price or portion of total sales) and only one found positive effects on PI [84].
Another important independent variable in the sample is fit or congruency, which refers to the relation between the company and the cause (or other variables). As Elving (2013) [54] explains, "a company might choose a CSR domain that is directly related to it-which is referred to as 'fit'-or one that is unrelated to it (p. 278)". There were three main types of fit found in the sample studies: company-cause fit [53], product-cause fit [53] and brand-cause fit [87]. Company-cause fit yielded positive outcome in three, yet mixed results in another three studies. Similarly, three studies that evaluated product-cause fit found positive results while five studies found mixed or not significant effects. Additionally, two brand-cause fit evaluations yielded positive effects while two studies were not significant.
On the other hand, the effect of the type of product and type of cause on PI was evaluated. The priority of hedonic product over utilitarian product on PI was found in one study [47], while opposite results were found in two studies and mixed effects in three studies. Similarly, the type of cause had positive effects on PI in only one study [52], while not significant effects were found in two studies. Finally, having the choice of cause to contribute to and the effect on PI was also assessed [85]. Only one study found positive results while the rest found mixed effects [70]. Further independent variable effects on PI were evaluated, and can be found in Table 3.      4. positive of donation type: cash > product; 5. positive of brand type: luxury > value; 6. positive of message type: textual claims including visuals > excluding visuals; 7. positive of fit type: taxonomic > thematic; 8. positive of donation framing: percentage of profit > percentage of price; 9. positive of donation source: company pays > own money. Fit: The Fit category includes the variable named as "congruency", "matching" in several studies. Donation amount: include the variable named as "donation size", "donation magnitude". CRM: cause-related marketing; CRMP: cause-related marketing program; CSR: corporate social responsibility.

Discussion
CRM is a globally popular marketing technique due to its value to multiple stakeholders such as the companies, the consumers, the non-profit organizations, and society [20,24,100]. Consumers' participation in purchasing related products or services, is the key to successful CRM practices [56]. Experiments on what factors can impact the effect of CRM have been conducted with a multitude of different determinants and their inter-relationships. This study thus provided a systematic review of experimental CRM research that measured PI. More specifically, this study provides a comprehensive overview of what the common CRM practices are and how other determinants can impact the effects of CRM on consumer PI. The main findings and recommendations in terms of CRM practices and research are below.
Firstly, the CRM in most qualified studies is manipulated as a tactical marketing program, which make a monetary donation and continues for a short time. This is consistent with the initial practice that firms generally assign greater importance to product sales (tactical, short-term outcome) than to improving/building image (strategic, long-term outcome) [101]. However, with the increase in the company's experience with CRM, strategic and social outcomes are assigned more importance and become equally important with PI [20]. Thus, companies should consider including CRM campaigns into their long-term marketing strategies. On the other hand, future research can empirically examine or systematically review the effect of CRM on consumer brand loyalty, recommendation intention, etc.
Secondly, substantial diversification was observed within the products and the causes. The products are mainly low-cost, low involvement, such as shampoo and chocolates. The high-familiar, high-involvement causes (e.g., educational, environmental, health) are supported by more companies, more frequently than the low-familiar, low-involvement causes (e.g., animal, cultural). Over time, the high-involvement causes will be more and more familiar with the public, and vice versa for the low-involvement causes [19]. This does not align with the sustainable development, which argues that every social issue is vital [102]. Therefore, marketers should also make efforts to improve people's awareness to the low-familiar, low involvement social causes.
Thirdly, this review also found that the theory use in CRM was heterogenous. Popular behavioral explanatory theories such TPB and social cognitive theory was seldom used. Most of the theories were used to explain how CRM works but did not specify how to utilize the theory to maximize the effects of CRM. For example, in the review by Christofi et al. (2018) [103], the authors argued that social exchange theory can explain the cause proximity in CRM as consumers identify with firms which can fulfill their self-enhancement. Other theories such as social identity theory or ELM serve the same purpose. Future research can consider experiments with theoretical constructs (e.g., self-efficacy, norms, etc.) to test whether theory use can boost the effects of CRM.
Fourthly, a substantial amount of studies demonstrated the effectiveness of CRM. In particular, the presence of CRM was proven to increase consumer PI toward the product or service. In addition, CRM is more effective than an ordinary marketing or sales promotion strategy, such as a discount and coupons. Furthermore, the specific characteristics of the CRM program (e.g., donation amount, cause type, message framing) have shown positive outcomes but mixed effects are persistent. For example, the mostly studied variable [23], cause-brand fit can have a positive, negative, or nonsignificant effect on consumer PI when varying company reputation [50]. Companies thus should carefully evaluate CRM campaigns with diverse donation formats before implementation to tailor specific characteristics that would appeal to target audiences with diverse values and backgrounds.
Fifthly, there is also little customization observed in the included studies. A customization strategy allows customers with heterogeneous preferences to be related with the product. With the advancement of interactivity in smartphones and internet, there exists more channels for the company to interact with the customers in order to offer more diversified and more customized types of causes and types of donations. For example, the customers will be able to select the cause they find most affiliated with, or the amount they wish to donate, based on certain criteria were met (e.g., the volume of sales exceed certain amount), which are extremely popular on modern crowdfunding platforms (e.g., kickstarter) but were seldom implemented in the CRM discipline.

Conclusions
To draw a comprehensive narrative evidence for the effectiveness of a CRM campaign, this study systematically reviewed the CRM literature that measured consumers PI using the experimental methodology. This research makes several contributions to the CRM literature. First, it presents a comprehensive review of the experimental study on CRM and, in line with Lafferty et al. (2016) [20], the categorization of diverse independent variables that affect PI. In contrast with other systematic reviews [20,23,34], this research focuses on one of the main marketing strategy goals, PI, providing researchers and practitioners with focused insights of the effectiveness of diverse CRM variables that they may employ in their campaign design. Second, it draws a compressive picture of current CRM practices, including the company/brand, product, cause, and donation information. Previous review articles about CRM mainly focus on characteristics of the company, product, and cause, such as how corporate reputation (high/medium/low), product type (hedonic/utilitarian), and cause-brand fit (high/low) impact consumer response to and the effectiveness of CRM. Our study also presents the specific product (e.g., shampoo, chocolate) and social cause (e.g., environmental, healthy) by extracting the components of the CRM campaign in the experiment. This, on the one hand, could guide the experiment design of future research in this field. On the other hand, this provides guidance for brand managers to design and communicate CRM programs in order to achieve more effective CRM campaigns which in turn will benefit multiple stakeholders and the whole world's sustainability in the long term.
Although this research has enabled us to paint a compressive picture of what current CRM practices are and their effectiveness, we cannot avoid its limitations: firstly, this study only provides a comprehensive narrative evidence synthesis, and does not generate one overall estimate of effect, such as calculating the heterogeneity metrics. Future studies could consider using the method of meta-analysis to assess heterogeneity of difference cause-related marketing experiments as well as providing quantifiable insights on the impacts of CRM on customer purchase intention. Secondly, this study adopted purchase intention rather than the actual purchase behavior to represent the effectiveness of CRM, although the purchase intention is the most direct predictor of purchase behavior. Future research could examine consumers actual purchasing behavior by observing and calculating consumers choosing behavior toward CRM-related product with different determinants. Thirdly, this study found that the majority of the determinants are micro-level factors, such as corporate, product, and social cause, etc. How about the macro-level factors? For example, is CRM strategies correlated with the socio-economic characteristics of the different countries? Future research could explore and answer this question. Finally, the results revealed that majority of the factors are related with CRM campaign content (cause, product, etc.) and/or communication (CRM ads), while little attention is paid to the information disclosure (e.g., the total donation amount and how they are spent) about CRM. Future studies could explore what and how the factors of CRM information disclosure impact consumer response.
Funding: This research received no external funding.

Conflicts of Interest:
The authors declare no conflict of interest.