Big data technologies change the way in which data and labor combine to create knowledge. Is this a modest innovation or a data revolution? Using hiring and wage data, we estimate firms’ data stocks and their knowledge production functions. Quantifying changes in production functions informs us about the likely long-run changes in output, in factor shares, and in the distribution of income, due to big data technologies. For the investment management industry, our structural estimates predict a 5% decline in the labor share of income; that change is comparable to similar estimates for the industrial revolution.