NEW YORK (MarketWatch) — The ICE U.S. Dollar Index finished the week lower Friday, after weaker-than-expected fourth-quarter gross domestic product data weighed on the greenback.

The index, a measure of the dollar’s strength against a trade-weighted basket of six rival currencies, finished the week at 94.87, down 0.1% from last Friday’s close

The dollar’s weekly loss wrapped up one of the most volatile months in the history of the foreign-exchange market.

“The euro, Swiss Franc, Australia and New Zealand dollars saw changes in excess of 5%, which is typically a fluctuation that you would expect over three to six months and not one month,” said Kathy Lien, managing director at BK Asset Management.

Last January, the average change in the major currencies was approximately 1.5%, Lien wrote.

One of the more embattled currencies, the ruble fell to a record low against the dollar Friday after the Russian Central Bank surprised the market by cutting its key interest rate by two percentage points to 15% from 17%.

The dollar rose USDRUB, +0.88%  to a record high of 72.51 rubles in early trade, before recovering to 69.65 rubles to the dollar. The greenback was worth 68.17 rubles Thursday evening. The central bank said it cut rates to curb rapidly rising consumer prices and to stimulate economic growth, which has been cratering since April.

The threat of fresh sanctions from the European Union also contributed to the ruble’s decline, as a gathering of European Union foreign ministers prepared to vote on extending the blacklisting of Russian separatist leaders from March until September, and adding new names to the list.

The central banks of both Canada and Denmark have announced surprise rate cuts in the last week, joining a cohort of central banks around the world, including, most notably, the Swiss National Bank, that are turning to abrupt monetary policy shifts to weaken their currencies.

After a weak reading on November gross domestic product growth, the Canadian loonie fell to a six-year low against the dollar.

The loonie has fallen 10% against the buck since the beginning of 2015. It’s recent losses are a remarkable turnaround from the demand for the currency in mid-2014, when the market expected the Bank of Canada to raise rates in the near future.

“Overall though, this has been an amazing turnaround for the CAD — a currency that was in demand as we entered the middle of last year because anticipation was high for the RBC to begin raising interest rates,” wrote Jameel Ahmad, chief market analyst for FXTM, in a research note Friday.

The loonie CADUSD, +0.00%  traded at 78.56 cents, just above a six-year low reached earlier in the session, compared with 79.30 cents Thursday.

Against the yen, the dollar extended losses from earlier in the session after the weaker-than-expected headline GDP growth number came in below expectations, before bouncing slightly as investors rushed to buy the greenback at lower levels.

The buck recently USDJPY, -0.64%  changed hands at ¥117.46 compared with ¥118.29 late Thursday in New York.