There is debate as to whether the early "Polish jokes" brought to states such as Wisconsin by German immigrants relate directly to the wave of American jokes of the early 1960s. A "provocative critique of previous scholarship on the subject" has been made by British writer Christie Davies in "The Mirth of Nations", which suggests that "Polish jokes" did not originate in Nazi Germany but much earlier, as an outgrowth of regional jokes rooted in "social class differences reaching back to the nineteenth century." According to Davies, American versions of Polish jokes are an unrelated "purely American phenomenon" and do not express the "historical Old World hatreds of the Germans for the Poles. However, Hollywood in the 1960s and 1970s imported the subhuman-intelligence jokes about Poles from old Nazi propaganda."