Much of what happens in the world is directly or indirectly the result of human decision. Improving decision-making (and skills, like forecasting, which aid in good decision-making) could therefore significantly improve the world.
One approach to improving decisions is to set up institutional structures that are conducive to good decision-making (Thaler & Sunstein 2008, Whittlestone 2017). This way, institutions like national governments might encourage people to make better decisions (e.g. saving for retirement) or make better decisions themselves (e.g. improving health policy).
Baron, Jonathan. 1988. Thinking and deciding. New York: Cambridge University Press.
Thaler, Richard & Cass Sunstein. 2008. Nudge: improving decisions about health, wealth, and happiness. New Haven, Conn.: Yale University Press.
Whittlestone, Jess. 2017. “Improving Institutional Decision-Making”. 80,000 Hours.