Definition: Answer the question from the given passage. Your answer should be directly extracted from the passage, and it should be a single entity, name, or number, not a sentence.
Input: Passage: In economics, notable Nobel Memorial Prize in Economic Sciences winners Milton Friedman, a major advisor to Republican U.S. President Ronald Reagan and Conservative British Prime Minister Margaret Thatcher, George Stigler, Nobel laureate and proponent of regulatory capture theory, Gary Becker, an important contributor to the family economics branch of economics, Herbert A. Simon, responsible for the modern interpretation of the concept of organizational decision-making, Paul Samuelson, the first American to win the Nobel Memorial Prize in Economic Sciences, and Eugene Fama, known for his work on portfolio theory, asset pricing and stock market behaviour, are all graduates. American economist, social theorist, political philosopher, and author Thomas Sowell is also an alumnus. Question: What university alumni member was known for his work on portfolio theory?
Output:
Eugene Fama