1. Introduction
The past decades since the reform and opening up have witnessed an intensifying aging of population and agricultural labor force in China [
1,
2]. According to the official estimate, the percentage of population aged and over 65 years old in China increased from 4.9% in 1982 to 11.4% in 2017 [
3]. Note that the aging population contributes greatly to the aging of agricultural labor force. In addition, a large number of young rural labor force have been entering the city, which further aggravates the aging of agricultural labor force in rural areas in China [
4]. In 1996, nearly 8.5% of the total agricultural labor force in China were aged over 60 years old, while it dramatically rose to 11.2% in 2006 [
5,
6]. A previous study predicted that the average age of agricultural labor force in China would further increase to about 55–56 years old in 2020 [
7].
In recent years, the consequences of aging of agricultural labor force have been attracting extensive attention, but the conclusions are mixed [
1,
8,
9]. In China, the aging of agricultural labor force and related impacts are the prominent issues of rural and agricultural development [
1]. Some studies argued that the aging of agricultural labor force is detrimental to agricultural production [
1,
10,
11]. Yang et al. found that land use efficiency would first increase and then decrease as the age of farmers grows, and there exists a negative impact of aging of agricultural labor force on land use efficiency [
12]. Using Chinese Household Income Survey (CHIP) in 2013, Zhang analyzed the impact of aging of agricultural labor force on land conversion, and found that the aging of agricultural labor force leads rural households to rent out but not to rent in the cultivated land, which in turn is not conducive to agricultural development [
13]. Yang employed an ordered probit estimation to investigate the impact of aging of agricultural labor force on technology adoption based on rural household survey data collected in the Yangtze River Basin in China, and the results showed that the aging of agricultural labor force is detrimental to adoption of green technologies in agriculture [
14]. Similarly, Wei and Xia argued that the aging of agricultural labor force has significantly negative impact on grain output using data from the main grain-producing regions during the period 2001–2015 [
15].
However, some studies concluded that there is not a significantly negative impact of the aging of agricultural labor force on agricultural production in China. Hu and Zhong pointed out that there is no significant difference of factor inputs in grain production between the young and elderly farmers, and thus, the aging of agricultural labor force has no negative impact [
8]. Using panel data of 186 rural households in Zhejiang Province from 1995 to 2006, Lin and Deng concluded that the aging of agricultural labor force does not exert significant impact on land use efficiency [
16]. Li et al. analyzed the impact of aging of agricultural labor force on agricultural production in China, and concluded that while the aging of agricultural labor force intensifies the shortage of local agricultural labor force, it could then promote technological evolution, which may exert a positive impact on agricultural production [
17].
Improving technical efficiency is a core issue in agricultural production, and a growing body of literature focuses on the relationship between aging of agricultural labor force and technical efficiency in China. However, the conclusions are also not consistent. Some studies found an inverted U-shaped relationship between age of agricultural labor force and technical efficiency, and reached a conclusion that the aging of agricultural labor force would worsen technical efficiency in agriculture [
2,
18,
19]. These studies mainly focus on the overall agriculture and grain production. Using survey data covering 745 apple-producing households in Shaanxi and Gansu provinces in China, Qiao et al. argued that there exists an inverted U-shaped relationship between age of farmers and technical efficiency in apple production, and the turning point of age is between 50 and 54 years old [
9]. By contrast, Zhou et al. had a different finding that there is no significant difference of technical efficiency in rice production between the young and elderly farmers, and the aging of agricultural labor force does not exert a negative impact on technical efficiency in rice production at the current stage [
20]. Similarly, Peng and Wen also concluded that the aging of agricultural labor force does not reduce technical efficiency in grain production nationwide [
21]. Moreover, Guo and Zuo pointed out that compared with the young agricultural labor force, the elderly show significant advantage in improving technical efficiency in grain production [
22].
While a considerable number of studies have investigated the consequences induced by the aging of agricultural labor force, little is known about the impact of aging of agricultural labor force on technical efficiency in tea production, especially in the mountainous areas of southwestern China. To fill the gap, this study aims to investigate the impact of aging of agricultural labor force on technical efficiency in tea production in the mountainous areas of southwestern China. The motivations are twofold. First, the previous studies regarding the relationship between aging of agricultural labor force and technical efficiency mainly focused on the overall agriculture, and grain production [
20,
21,
22]. In China, grain crops, such as rice and wheat, are mainly grown in plain area, which facilities the large-scale production and adoption of agricultural machinery. The impact of aging of agricultural labor force can be largely offset by scale effect and mechanization. In the context, the impact of aging of agricultural labor force on technical efficiency in grain production may not be significant as argued in much literature [
20,
21,
22]. However, this study focuses on tea production in the mountainous areas of southwestern China where it is extremely difficult to promote the large-scale production and adoption of agricultural machinery. Given the fact that tea production is labor intensive, the impact of aging of agricultural labor force on technical efficiency in tea production in the mountainous areas of southwestern China would be quite different. Second, China has been making great efforts to promote the comprehensive poverty alleviation, especially in the southwestern mountainous areas. It should be noted that tea production constitutes a main income source of a large number of farmers in the mountainous areas of southwestern China. During the past decades, meanwhile, a large number of agricultural labor force in the mountainous areas of southwestern China have been migrating to the eastern and coastal areas for higher return to labor, which greatly aggravates the aging of agricultural labor force in the southwestern mountainous areas. In such context, this study focuses on the impact of aging of agricultural labor force on technical efficiency in tea production in the mountainous areas of southwestern China, which is expected to provide several policy implications for meeting the challenges from aging of agricultural labor force, and promoting tea production and income growth of farmers in the mountainous areas.
In this study, we first develop a theoretical analysis about the impact of aging of agricultural labor force on technical efficiency in tea production, and then empirically investigate the impact of aging of tea-producing farmers on technical efficiency in tea production using a cross-sectional survey data covering a total of 241 tea-producing rural households in Meitan, a main tea-producing county located in Guizhou Province in the mountainous areas of southwestern China. The results in this study support that there exists an inverted U-shaped relationship between age of tea-producing farmers and technical efficiency in tea production, and the turning point of the age is about 43 years old. Given the fact that the sampled farmers averagely aged over 50 years old and more than 83.4% of them are aged and over 43 years old, this study reveals that the aging of agricultural labor force has a negative impact of technical efficiency in tea production. Overall, this study contributes to the literature from two aspects. First, we provide a theoretical analysis about how the aging of agricultural labor force influences technical efficiency in tea production, which forms the solid foundation for the empirical analysis. Second, this study focuses on tea instead of grain crops. As mentioned, the previous studies mainly examine the relationship between aging of agricultural labor force and overall agriculture or grain production, of which the conclusions and the interpretations are limited and not enough to reveal the actual impact of aging of agricultural labor force on agricultural production. Hence, this study enriches the literature by focusing on tea production.
The following parts of this study includes four sections.
Section 2 first develops a theoretical analysis about the impact of aging of agricultural labor force on technical efficiency in tea production, and then provides the research hypothesis. In
Section 3, a stochastic frontier production function used to calculate technical efficiency and analyze the impact of aging of agricultural labor force on technical efficiency is constructed, and data source is described. The econometric results with robustness tests are presented and discussed in
Section 4. In addition,
Section 5 concludes with policy implications.
2. Theoretical Analysis
The output growth of crops depends mainly on factor inputs, such as fertilizer, pesticide and irrigation, and the adoption of good technologies. In modern agriculture, it has been frequently documented that the adoption of technologies and technical efficiency play crucial roles in promoting agricultural output growth [
23,
24,
25]. That is, the wholly efficient utilization of the adopted technologies could result in the maximum output given the certain factor inputs. Hence, technical efficiency is often used to measure whether the best available technologies are adopted and efficiently utilized in agricultural production [
26]. In general, the best available technologies are adopted and efficiently utilized if technical efficiency equals one. Otherwise, there might be some loss of technical efficiency. Much literature pays attention to the determinants of technical efficiency in agriculture [
24,
26,
27,
28], among which were a growing number of studies focusing on the aging of agricultural labor force [
2,
9].
The impact of aging of agricultural labor force on technical efficiency in tea production might depend on the experience effect and physical effect. In this study, better experience (a proxy of knowledge and skills about tea production) and physical strength would contribute to the adoption and more efficient utilization of better technologies [
9]. Hence, it is reasonably assumed that better experience and physical strength would in turn induce higher technical efficiency in tea production [
2,
8]. Let
TE,
E,
P, and
C denote technical efficiency, experience, physical strength, and other factors influencing technical efficiency, respectively. The technical efficiency function in tea production could be developed as:
It should be noted that both experience and physical strength could be treated as the functions of farmers’ age, denoted by the term
A in this study. As farmers become older, the knowledge and skills represented by the experience would be improved, which could contribute to the adoption and efficient utilization of better technologies. However, physical strength would unavoidably decline as farmers’ age increases, which is detrimental to the adoption and utilization of better technologies. In the context, the following equations are obtained:
According to the analysis above, the impact of farmers’ age on technical efficiency could be described by the first derivative as follows:
Combined with Equations (2)–(5), the part before the plus sign on the right side of Equation (6) is positive, while the other part after the plus sign is negative. Hence, it is not explicit to identify whether the impact of farmers’ age on technical efficiency is positive or negative. When farmers are relatively young, the improvement of experience of tea production would be prominent, while the decline of physical strength due to the increase of farmers’ age would be limited. In the context, the impact of farmers’ age might be overall positive. However, when farmers become relatively old, the increase in farmers’ age would not result in obvious improvement of experience of tea production, but the continuous decline of physical strength would greatly hinder the adoption and utilization of technologies, which is harmful to technical efficiency. Hence, we assume that the positive experience effect would be more important than the negative physical effect when farmers are relatively young, while the negative physical effect would gradually play a more important role when farmers are relatively old. In sum, a potential inference is that technical efficiency in tea production would first increase and then decrease as farmers’ age grows.
In fact, the effects of experience of tea production and physical strength should not be treated as linear. Indeed, the knowledge and skills of tea production would probably increase at a diminishing rate as farmers’ age increases. By contrast, physical strength of farmers would then decrease at an increasing rate. As a result, we could obtain the second derivatives of the experience and physical strength on farmers’ age as:
Hence, the second derivative of technical efficiency in tea production on farmers’ age could be derived as follows:
As show in Equation (9), it is apparent that the sign of the second derivative is negative, which once again confirms the inference analyzed above. Hence, the hypothesis of interest to be validated in this study is that although there might exist an inverted U-shaped relationship between farmers’ age and technical efficiency in tea production, the impact of aging of farmers on technical efficiency would be negative.
5. Conclusions and Policy Implications
Since the reform and opening up, China has seen an intensifying aging of population and agricultural labor force. During the past decades, the aging of agricultural labor force and its impact on agricultural production have been attracting extensive attention. However, the conclusions of the previous studies are mixed. In addition, little is known about the relationship between aging of agricultural labor force and technical efficiency in tea production especially in the mountainous areas of southwestern China. It is notable that tea is a typically labor-intensive cash crop greatly different from grain crops. This study first constructs a theoretical analysis that illustrates how the aging of agricultural labor force influences technical efficiency in tea production. Using the stochastic frontier analysis and cross-sectional survey data covering 241 tea-producing farmers in Meitan County in China, the econometric results of this study show that there might exist an inverted U-shaped relationship between farmers’ age and the technical efficiency index. In the actual context of the sampled tea-producing farmers in China, our finding provides robust evidence that the aging of tea-producing farmers exerts significantly negative impact on technical efficiency in tea production in China. Moreover, the total area of tea orchards, distance from home to village committee, and township location are also significantly associated with the technical efficiency in tea production.
In the context of meeting the challenges from aging of agricultural labor force and mitigating the negative impact of aging of agricultural labor force on technical efficiency in tea production in China, the findings in this study have several important policy implications. First, more efforts should be made to attract and encourage rural–urban migrants to engage in tea production. As well documented in previous studies, return migrants have been playing an increasing role in agricultural production, and often perform better than those non-migrants [
46,
47]. In the context of the aging of tea-producing farmers, return migrants could become crucial alternatives to those non-migrants for tea production, which might be conducive to improving technical efficiency in tea production. Second, technology extension should be enhanced, and shifted from only introducing new technologies to both introducing new technologies and improving the utilization efficiency of technologies. The negative relationship between the distance from home to village committee and technical efficiency illustrates that better access to agricultural technology extension could improve technical efficiency in tea production. Hence, a strengthened public agricultural extension system as well as socialized agricultural service system is expected to play a crucial role in promoting the increase in technical efficiency. Third, the government is also expected to regulate land conversion to avoid irrational expansion of tea orchards. This study shows that there might be a negative impact of total area of tea orchards on technical efficiency, which means that irrational expansion of tea orchards is detrimental to technical efficiency. In the context, the government should take feasible measures to avoid irrational expansion of tea orchards.
Overall, there exist several methodological drawbacks in this study. First, the rural household survey was not conducted in Guizhou, which to some extent may limit the generalization of the conclusions in this study. Second, some interesting variables are omitted due to the data unavailability. For example, the share of elderly household laborers, a suitable alternative that describes the aging of agricultural labor force, was not taken into account in this study because the survey did not contain the related question. Another variable, land quality, is an important factor influencing tea yield that was also not included since the cost to test land quality is too high.