Kenneth Arrow, who has just passed away, was a giant in economics. His contributions started nearly 70 years ago, and he remained active until the end of his life. For example he debated Thomas Piketty’s views on inequality, advocating that we should pay more attention to inequalities in consumption than in income and wealth.
In 1972, he was awarded the Nobel memorial prize in economic theory at the age of 51, (still) the youngest ever recipient. The Nobel-winning game theorist Robert Aumann is quoted in the Washington Post’s obituary as saying that “in the second half of the 20th century [Arrow] absolutely had more of an impact than anyone else” on economic theory.
To see why this is not an exaggeration, consider that two seminal contributions Arrow made when he was barely 30 — one on his famously eponymous “impossibility theorem” for collective choice, the other on the conditions for “general equilibrium” in which all markets simultaneously match supply and demand — were not just remarkable insights on their own, but set agendas for economics research that remain unexhausted.