@article{Clark2007,
author = {Clark, T. and Hatton, T.J. and Williamson, G.J.},
title= {Explaining U.S. immigration, 1971-1998},
year = {2007},
doi = {10.1162/rest.89.2.359},
journal = {The review of Economics and Statistics},
volume = {89},
number = {2},
pages = {359--373},
}