Is Momentum an Echo?

In the United States, momentum portfolios formed from 12 to 7 months prior to the current month deliver higher future returns than momentum portfolios formed from 6 to 2 months prior, suggesting an echo in returns. In 37 countries excluding the United States, there is no robust evidence of such an echo. In portfolios that combine securities in developed and emerging markets, or across three major geographic regions (Americas excluding United States, Asia, and Europe), there is also no evidence of an echo. Any echo in the United States appears to be driven largely by a carryover of short-term reversals from month - 2.