A market's efficiency would increase if traders who is less informed than the average starts index investing instead of trading (poorly). If traders who actuall

A market's efficiency would increase if traders who is less informed than the average starts index investing instead of trading (poorly). If traders who actually have more information than average go into index investing, you actually might lose market efficiency (by not trading positions that they could profit off more than passive investing). An increase in market efficiency means the prices of the equities match their true value faster.