Mean Reversion and Momentum in Central and Eastern European Countries ¨C A Case Study on Poland and Romania

There is considerable evidence showing that both mean reversion and momentum exist in stock prices, especially in financially-developed countries. We analyze these phenomena for two Central and Eastern European countries with very different transitions from centrally-planned to market economies- Poland and Romania. Although Poland’s stock market cannot be considered well-developed, its capitalization increased from 3 percent of GDP in 1995 to about 30 percent in 2017, while Romania’s stayed under 6 percent of GDP in the 1990s and early 2000s, and only recently has increased to about 21 percent. Examining how mean reversion and momentum affect stock prices, we find very similar results for the two countries. The speed at which stocks converge back to their fundamentals (i.e., mean reversion) is much faster than that of the developed markets, with half-lives of just over 9 months for both countries (similar to the results obtained in the literature for the Chinese market, but much shorter than the 3-4 years for the well-developed markets). We also find that the momentum effect lasts less than in the developed countries. Therefore, in most cases, strategies combining mean reversion and momentum generate abnormal excess returns only for holding periods of less than 12 months.