# Price Index 1M

Last month's winners are next month's losers. In his paper Evidence of predictable behavior of security returns, Narasimhan Jegadeesh reported a strong negative correlation between returns in subsequent months. He examined stock returns in the period 1934-1987 and found that prior month winners have an average next month return of -1.38%, while the prior month's losers have an average (next month) return of 1.11%. The gap is 2.49%. The author concludes:

The results documented here reliably reject the hypothesis that stock prices follow random walks. Predictability of stock returns can be attributed either to market inefficiency or to systematic changes in expected stock returns.

Formula:

$Price Index 1M = Adjusted* share price now Adjusted* share price 1 month ago$

* The share price is adjusted for stock splits, cash dividends, right offerings and spin-offs.