Kenneth Arrow was an American economist who was awarded the Nobel Memorial Prize in Economic Sciences in 1972 for "pioneering contributions to general economic equilibrium theory and welfare theory". His work has been pivotal in the development of modern microeconomics, macroeconomics, and social choice theory.

Arrow studied at the University of Columbia, where he gained a master's degree in mathematics in 1940 and a PhD in Economics in 1951. During his studies, he was heavily influenced by noted economists like Frank H. Knight and Oskar Lange. After the completion of his studies, he went on to teach at universities such as the University of Chicago and Stanford University.

One of Arrow's hallmark accomplishments is his work on the Arrow Impossibility Theorem. This theorem states that it is impossible for every voter's preferences to be accurately represented in a ranked-choice voting system. This theorem earned Arrow his Nobel Prize, and is studied presently in economics, voting theory, and decision theory classes alike.

In addition to his policies on social choice theory, Arrow also had a great impact in terms of macroeconomics and microeconomics. In terms of macroeconomics, Arrow put forth important theories related to the stability of economic systems and the detriments of macroeconomic fluctuations. On the microeconomic front, his contributions include his work on the Arrow-Debreu model of general equilibrium theory and the overall expansion of the analytical tractability of models in the field of economics.

During his lifetime, Arrow also served on several distinguished committees, such as the US-Japan Joint Committee on Trade and Investment, along with former US President Jimmy Carter and economist Paul Samuelson. He was also an outspoken critic of the Vietnam War and apartheid in South Africa and often voiced his opinions on political and economic television shows.

In conclusion, Kenneth Arrow was one of the most influential economists of the twentieth century. His work has been instrumental in the development of modern economics, and his awards and honors are a testament to this influence. His theories, models, and theses are still being sought after by economists, mathematicians, and even political theorists alike. With this body of work, Arrow has left an enduring legacy in the field of economics.