There's a good rule that gives us a clue: the 10-month average rule. This tells us we should buy when prices are above their 10-month average and sell when they are below it. This rule works for US and UK equities, for gold and for bubble-prone sectors. It should not, therefore, be a surprise that it also works for emerging markets.
My table shows the point. It shows what would have happened if you had followed this rule for the MSCI emerging market index since December 1990. At the end of each month, you buy the index if it is above its 10-month average, and you hold one-month dollar deposits if it is below it.