Semiparametric Small Area Estimation of Crop Acreage under Partially   Linear Model
  Small area estimation under linear mixed models often assumes that the small area effect is random effect in almost all previous studies. However, in this paper a new approach is proposed explaining small area effect as the unknown function of an area-indicative variable, which is a kind of semiparametric models. The nonparametric part for area effect is represented by using penalized splines, from which the estimation and inference are done in the linear mixed model framework. The mean-squared error of empirical estimators is shown, and the testing for small area effect also considered. Additionally, some numerical simulations are demonstrated to express the good performance of this method. 
Rong Zhu and Guohua Zou and Chun Wang and Yi Hu
stat.ME