1.   Last June and July, for instance, Russia lifted most restrictions on trading the ruble.

2.   On Thursday, dollars were scarce as Russians clamored to trade their rubles for a safe-haven currency.

3.   The lunge for dollars was driven mostly by Russian banks that scrambled to trade rubles for dollars and other foreign currencies.

4.   This year, the government set rate limits for trading the ruble, largely to prevent such instability.