An efficient hybrid approach of quantile and expectile regression

Abstract: Quantiles and expectiles are determined by different loss functions: asymmetric least absolute deviation for quantiles and asymmetric squared loss for expectiles. This distinction ensures that quantile regression methods are robust to outliers but somewhat less effective than expectile regression, especially for normally distributed data. However, expectile regression is vulnerable to lack of robustness, especially for heavy-tailed distributions. To address this trade-off between robustness and effectiveness, we propose a novel approach. By introducing a parameter $\gamma$ that ranges between 0 and 1, we combine the aforementioned loss functions, resulting in a hybrid approach of quantiles and expectiles. This fusion leads to the estimation of a new type of location parameter family within the linear regression framework, termed Hybrid of Quantile and Expectile Regression (HQER). The asymptotic properties of the resulting estimaror are then established. Through simulation studies, we compare the asymptotic relative efficiency of the HQER estimator with its competitors, namely the quantile, expectile, and $k$th power expectile regression estimators. Our results show that HQER outperforms its competitors in several simulation scenarios. In addition, we apply HQER to a real dataset to illustrate its practical utility.