Studies focusing more narrowly on the U.S. labor movement corroborate the comparative findings about the importance of structural factors, but tend to emphasize the effects of changing labor markets due to globalization to a greater extent. Bronfenbrenner notes that changes in the economy, such as increased global competition, capital flight, and the transitions from a manufacturing to a service economy and to a greater reliance on transitory and contingent workers, accounts for only a third of the decline in union density.