Investors and policy makers have historically had a tough time predicting the precise moment when a neighborhood is about to start gentrifying.

It turns out that Yelp reviews for everything from cafes to barber shops might offer a solid clue, according to researchers at Harvard University.

Pinpointing a turn toward sharply higher prices can be advantageous for a range of parties, from investors looking to cash in to city managers eager to curtail price jumps, said Michael Luca, an associate professor of business administration at Harvard, whose research focuses on online businesses.

The research, based on data provided by online review company Yelp Inc., could allow policy makers to identify earlier on the neighborhoods to target to preserve existing low-cost housing, for example.

Current tools for predicting gentrification are limited and often yield insights long after the results are obvious to anyone taking a casual stroll in a neighborhood.