The paper introduces a novel approach to testing for unit roots in panels. Following Chang and Park (2004), the approach takes a new contour that is drawn along the line given by the equi-squared-sum instead of the traditional one given by the equi-sample-size. As we show in the paper, the...

This paper considers the regression with errors having nonstationary nonlinear heteroskedasticity. For both the usual stationary regression and the nonstationary cointegrating regression, we develop the asymptotic theories for the least squares methods in the presence of conditional...