lllustates the sampling process of the present study. The sampling involved four stages. In the first stage, with counties as the sampling frame, we randomly selected two counties from Lian Yungang City. Then, with towns within the two counties as the sampling frame, we chose six towns for the two counties at random. Afterwards, using the same sampling method as in the second stage, a total of 18 villages were chosen. At last, we used systematic random sampling methods to select 360 households.