what did markowitz call his a ha moment 
markowitz s a ha moment came when he was reading a book on mathematical probability and he had his famous brainstorm about risk correlation that the volatility of the portfolio depends not only on the volatility of the constituents but to what extent they go up and down together 3the bottom linesince he developed modern portfolio theory mpt in 1952 harry markowitz has been one of the most important pioneers of the new field of financial economics his groundbreaking work on concepts ranging from portfolio theory to computer programming language laid the foundation for how wall street operates today markowitz s work has also popularized concepts like diversification and overall portfolio risk and return shifting the focus away from the performance of individual stocks 