The fraction of national income accruing to labor (the labor share) had been roughly constant in developed economies for much of the 20th century but has fallen since the 1980s. We review several of the leading explanations in the literature for the declining labor share. We then point to hitherto unexplored dimensions of the data and provide suggestive evidence for a new explanation. In particular, we show that the labor share began a steeper descent in 2000. This more recent break in the labor-share trend coincides with the rapid rise of software investment, which has left a larger impact on service industries (than manufacturing) and on high-skill, cognitive occupations (than middle-skill, routine occupations).