The American Revolution severely limited immigration to the United States, but economic historians dispute its long-term impact. Sharon Salinger argues that the economic crisis that followed the war made long-term labor contracts unattractive. His analysis of Philadelphia's population shows how the percentage of bound citizens fell from 17% to 6.4% over the course of the war. William Miller posits a more moderate theory, stating that "the Revolution...wrought disturbances upon white servitude. But these were temporary rather than lasting". David Galenson supports this theory by proposing that the numbers of British indentured servants never recovered, and that Europeans from other nationalities replaced them.