Robert M. Solow, who won a Nobel in economic science in 1987 for his theory that advances in technology, rather than increases in capital and labor, have been the primary drivers of economic growth in the United Stated, died on Dec. 21 at his home in Lexington, MA. He was 99.

Professor Solow taught at the Massachusetts Institute of Technology, where he and a fellow Nobel laureate, Paul A. Samuelson, forged the M.I.T. style of economic analysis, which emerged as a leading approach in the second half of the 20th century and played an important role in economic policymaking.

Although choice posts in Washington beckoned  — he did serve briefly as a staff member of the president’s Council of Economic Advisers during the Kennedy administration — Professor Solow’s heart was always in academia. Once, when invited to an embassy party, his secretary was asked his rank so he could be properly seated according to protocol. “Tell them,” he told her, “I’m a full professor of economics at M.I.T. — and they don’t have anything that high in the government.”