Ordinary investors don’t stand much chance of beating the market. It moves way too fast and efficiently. Or it behaves in ways that make no sense at all.

Three Americans won the Nobel prize in economics Monday for their sometimes-contradictory insights into the complexities of investing.

Eugene Fama and Lars Peter Hansen of the University of Chicago and Robert Shiller of Yale University were honored for shedding light on the forces that move stock, bond and home prices — findings that have transformed how people invest.

Fama’s research revealed the efficiency of financial markets: They absorb information so fast that individual investors can’t outperform the markets as a whole. His work helped popularize index funds, which reflect an entire market of assets, such as the Standard & Poor’s 500 stock index.

Shiller’s research examined asset prices from a contrasting angle. He showed that in the long run, stock and bond markets can behave irrationally, reaching prices that are out of whack with economic fundamentals.

Shiller, 67, predicted the dot-com crash of the early 2000s and the implosion of home prices in 2007.

Hansen has focused on statistical models, creating ways to test competing theories of why asset prices move as they do.