This paper examines how unions affect the rate of productivity change over time. The direction of union impact cannot be predicted from economic theory. Firms may tend to select more productive technologies to offset the cost of higher union wages or they may tend to select less productive technologies to keep union wage demands in line. Evidence from manufacturing indicates that unions have not affected productivity growth, but in the construction industry productivity growth has been much

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... er in areas where there is a high initial level of unionization or where unionization is growing.