Summary: While labor's share of world GDP is over one half, capital's share is close to one third. When considering altruistic interventions to increase economic output, as in GiveWell Labs' exploration of U.S. policy, efforts to increase saving and investment should be considered alongside efforts to improve effective labor supply. Compulsory savings schemes and government savings schemes have been used in other developed countries to induce savings far above U.S. levels, and global adoption of such schemes could produce annual gains of many trillions of dollars, although the potential gains are substantially less than the potential gains of labor mobility. Regulatory changes to default pension/investment contributions might also capture important, albeit smaller, gains.