Many of the rejections of the PIH emphasize the importance of liquidity constraints. This places a focus not on the PIH's behavioral assumptions, but rather on its ancillary assumption that consumers can easily borrow or lend. This insight has led to adjustments of the simplest PIH model to account for e.g. capital market imperfections. Some of these adjustments to the PIH, such as the buffer-stock version of Christopher Carroll (1997) have added further evidence supporting consumption smoothing. A comprehensive meta-analysis of 3000 tests of the permanent income hypothesis reported in 144 studies found that many rejections of the PIH are due to publication bias and that, after correction for publication bias, the PIH is consistent with data.