London: The Russian rouble is proving surprisingly impervious to the price of oil.

The currency of the world’s largest energy exporter has more or less ignored the value of the commodity in the past few months, according to Citigroup Inc. analysts led by Luis Costa.

Usually when oil prices fall, so does the currency, but not so recently:

Fair value for the currency is 68 roubles to the dollar, according to the analysts’ calculations — based on regression modelling of Brent crude futures and the dollar-rouble exchange rate.

The current level is more like 65.8.

The rouble has returned the most of any major world currency in 2016 after Brazil’s real and Japan’s yen, attracting investors searching for higher yields amid record central bank stimulus in developed nations.

It’s also the best currency for carry trades — which involve borrowing in low-interest rate currencies to buy higher-yielding ones — according to JPMorgan Chase & Co. and Goldman Sachs Group Inc.

A stronger rouble is a double-edged sword, however. While the currency’s gain has been good news for hot money investors who dip in and out of the market, it’s put a strain on Russia’s budget by shrinking the value of a barrel of oil in local-currency terms and depriving the government of revenue as it runs the widest deficit since 2010.

Yet the sword could soon be turned on the speculators.

Russian President Vladimir Putin last week drew attention to the rouble’s strength and instructed Prime Minister Dmitry Medvedev to pay attention to the currency’s moves relative to the volatility of oil. While a senior official says his comments were more a message for the government than the central bank, his remarks caused a tumble in the rouble and have prompted speculation that the Bank of Russia or finance ministry will take steps to weaken the exchange rate.

For hedge fund investors who have boosted long positions in the currency, now might be a good time to exit, the Citi analysts write:

“Further, verbal intervention from the Kremlin late last week has served as an early warning to the build-up of excessive carry positions in recent weeks. Indeed, CFTC positioning in RUB-longs are in extremely stretched territory. A lot of cuts have already been priced into the [rouble-denominated Russian government bonds] OFZ curve (which stands out as offering the lowest term premia in emerging markets currently), and real money investors might start looking to take profits on their positions ahead of seasonal weakness in RUB in the coming months.”