Due to the continuing expansion of the medical education in China , the aging of the healthcare workforce should not be a serious problem. In 2011, 68.3% of the licensed (assistant) doctors in hospitals and 73.0% of the licensed (assistant) doctors in the THCs were under 45 years of age; only 4.8% of the licensed (assistant) doctors in the hospitals and 3.2% of the licensed (assistant) doctors in the THCs were over 60 years of age according to the survey by the MOH . However, among the village doctors in our sample, 41.3% were younger than 45 years old, and 30.0% were more than 60 years old, which was consistent with other studies [40, 41]. The aging of the village doctors was partly due to the historical causes, as 45.3% of the village doctors were the barefoot doctors who started to work as a doctor before 1985, when the MOH began to use ‘Village Doctor’ to replace ‘Barefoot Doctor’ . As shown above, there was no national pension for the village doctors, so they had to practice at the village clinics until reaching 60 years old or even after 60 years old to earn a living. Even worse, few young medical graduates supplemented the rural health workforce due to low salary and fewer opportunities etcetera. As a consequence, the percentage of aging village doctors has increased.
Furthermore, counties with greater economic development had a higher possibility of having older village doctors. As shown in Table 2, the village doctors in Changshu and Liyang were much older than those in Jingning. A potential explanation was that the young in Changshu and Liyang had better chances for making money, whereas practicing medicine in Jingning was not a bad option, which attracted more young people to join the healthcare workforce in the underdeveloped areas.
Unlike the aging problem that existed in all counties, the gender imbalance might only be a problem in poor counties. In Changshu, Liyang, Mianzhu, and Yongchuan, the gender imbalance was not a real problem because female village doctors composed one-third of all village doctors, while in Jingning, only 6.3% of the doctors were female (male/female = 15.0). That was troublesome because most of the public healthcare services (including maternal and gynecological care) were delivered by the village doctors; unfortunately, customs often prevented women from seeking maternal and gynecological care from male village doctors .
In general, the western medicine, TCM and mixed methods were applied in all five counties, and mixed methods were the most frequently reported (58.5%), followed by the western medicine (38.5%) and TCM (3.0%). However, the constitutions of the practice methods in the sampled counties differed from each other. The village doctors in Changshu and Liyang were more likely to practice western medicine (44.6%), while the village doctors in Jingning preferred mixed methods (77.5%). This might be due to the different purchasing power of the rural residents in different counties; the GDP per capita in Changshu can be as high as 96,518 RMB, which is 26-fold greater than the 3,711 RMB GDP per capita in Jingning in 2010 [34, 37]. The village doctors in Changshu could provide more expensive and profitable western medical services to the consumers, while the village doctors in Jingning preferred mixed methods, which included less expensive TCM.
Similar to the results of the national statistics of village doctors, only 5.3% of the village doctors obtained a degree from junior college or higher, and 75.6% had only completed a secondary school education . The proportion of village doctors with a junior college degree or higher was much lower than that for licensed (assistant) doctors in hospitals (8.8% versus 79.4%) and the licensed (assistant) doctors in THCs (8.8% versus 51.5%) . It might be difficult to meet the goals set by the central government, which requires that all village doctors to have at least a secondary school degree by the end of the year 2015. Only 68.5% of village doctors had met that requirement in the year 2011.
We also found that the practice method was not correlated with the education level (P = 0.43), but closely related to the way of obtaining their highest education degree (P <0.01). Most of the curricula in China’s medical school were set for western medicine. Therefore, the village doctors who obtained their highest degree from medical school before beginning to work were more likely to practice western medicine, while the village doctors obtaining their highest degree through on-the-job training were more likely to practice mixed methods, as the mixed methods have been used to train the village doctors since the 1970s.
Good remuneration was regarded as a critical incentive for the recruitment and retention of healthcare workers in rural and remote areas [5, 7, 42–44], and it was also the major dynamic of the push-pull process of the domestic and international healthcare workforce migration [45, 46]. The average annual income of the physicians in our study was 21,804 RMB in 2011, which was almost equal to the disposable income of the urban residents (21,810 RMB) and three-fold greater than the net per capita income of the rural residents (6,977 RMB) in 2011 . If one takes the public health service bonus and other incomes from agriculture and other activities (for example, some village doctors have part-time jobs as couriers or drivers) into consideration, the total income for village doctors should be much higher than the income for common rural residents.
However, there are extremely large income gaps among village doctors in different districts. The highest income in our study was 40,000 RMB per month, while 74 village doctors earned less than 200 RMB per month. Actually, village doctors in rural China acted as private practitioners  and competed with other village doctors, private clinics and THCs after the collective economy collapsed, and their income was decided by the technique, relative advantages and local economic development. So it should not be surprising that huge income gaps exist among village doctors.
Being private practitioners rather than employees of the government, the village doctors could not enjoy the social protection provided by the government. In essence, the village doctors were treated almost the same as the farmers, although village doctors earned their living by providing medical services to rural residents. Rural residents in China lacked Social Pension Insurance before the State Council launched the New Rural Social Pension Insurance System (NRSPIS) in rural areas in 2009 . Therefore, the village doctors, like the rural residents, could receive 55 RMB per month, but they could not enjoy the additional pension provided by the government for their medical professional service at a national level. In this study, additional pensions were provided to the village doctors only in Changshu and Yongchuan, an effort intended to address the retirement of aging village doctors. Obviously, counties without additional pensions for older doctors might face these same challenges in the future, regardless of the local economic status.
This study, as a longitudinal study, might provide some fundamental knowledge on the current rural health workforce of China. However, a number of limitations of this study should be acknowledged. First, we did not test the validity or reliability of the questionnaires; however, the questionnaires were modified from the well-tested official ones, revised on the basis of focus group input, and their validity was improved with in-depth interviews and pilot surveys. Additionally, not all village doctors participated in this survey, and missing values existed in the data collection. However, 88% was a relatively high response rate, and missing values were very small and randomized. Last, but not least, the generalization of the results should be conservative because it was not a random representative sample of the population.
In the next phase of this study, Hailun County from Heilongjiang Province (northeast China) will be added into this project and more detailed study about the aging, training, and public health services of village doctors will be conducted. Furthermore, physical and mental health conditions of village doctors will also be investigated by survey.