“…A variety of other forms of heterogeneity have been studied using conventional regression analysis. For example, workers in more competitive industries report higher levels of happiness, possibly suggesting that competitive pressures lead firms to improve working conditions (Tiemann and Veglahn 1979). In an efficiency study of farmers in India, those who are older, own large or geographically fragmented land holdings, or have subsistence needs in addition to raising cash crops appear to be less efficient (Ali, Parikh, and Shah 1996).…”