“…The dependent variable, DlnNPWSHict is the percentage change of the non-production worker wage share of the wage bill in the four-digit SIC industry i in county c from time t -1 to t. Following Feenstra andHanson (1999, 1996) and Berman, Bound, and Griliches (1994), and others, non-production wage share is used as a measure of the relative demand for skilled labor. Non-production and production worker status categories found in industry accounts are widely used as proxies for skilled and unskilled workers, respectively (Berman, Bound, and Griliches 1994;Borjas, Freeman, and Katz 1992;Haskel and Slaughter 2002;Lawrence and Slaughter 1993;Leamer 1993;Sachs and Shatz 1994;Yan 2005). Although using production and non-production status as proxies for skill levels has received criticism in the literature for being an unreliable measure of skill classification (Forbes 2001), several other scholars have argued that, despite problems with the nonproduction/production classification, it provides clear and reliable results.…”