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US stocks rose, with the Dow and S&P 500 setting record highs and posting a sixth straight week of gains.
Janet Yellen's comments, interpreted as showing there would be no cut in Fed stimulus any time soon, sparked a rally in equity markets and dented the low-yielding yen, which typically falls when investors are willing to shoulder risk.
Yellen, now the Fed's vice chair, defended the US central bank's steps to spur economic growth and called efforts to boost hiring "imperative" at a hearing on Thursday on her nomination before the US Senate Banking Committee.
"There's a sincere expectation that monetary policy will be calibrated according to economic conditions," said Jeff Knight, head of global asset allocations at Boston-based Columbia Management, with $345 billion in assets under management.
"At least for now the Fed does not regard the impact of its bond purchases on asset prices as a reason to start tapering. There will be an analysis of economic conditions. That's important information," he said.
The Dow Jones industrial average closed up 85.48 points, or 0.54%, at 15,961.70. The S&P 500 ended up 7.56 points, or 0.42%, at 1,798.18. The Nasdaq composite index closed up 13.227 points, or 0.42%, at 3,985.968.
For the week, the Dow ended up 1.3%, the S&P 500 closed up 1.6%, and the NASDAQ composite index racked up a 1.7% rise.
"There's a general bias upward in asset prices because of the huge wall of bank reserves the Fed has put out there," said John Rutledge, chief investment strategist at Safanad, a New York City-based investment firm.
The dollar rose 0.23% to 100.26 yen, having hit a high of 100.43 yen that left it the potential to target the September 11 high of 100.60 yen.
The yen fell broadly, with sterling hitting a four-year high against the Japanese currency.
US Treasury notes, like the yen less desirable when investors are buying riskier assets, slipped 5/32, leaving its yield at 2.70%.
China on Friday announced a raft of reform plans, including accelerating capital account convertibility, but this had little impact on sentiment.
Against a basket of currencies, the dollar eased marginally to 80.808.
The euro was up 0.19% at $1.3485, below a one-week high of $1.3497 touched on Thursday.
It remains under pressure from the disparity between the US and European economies - underlined by weak euro zone GDP numbers on Thursday, which kept alive the possibility of more central bank action to stimulate growth.
The euro rose against the yen, however, hitting a two-week high of 135.08 yen.
An index of world equity markets marched higher after Yellen told the confirmation hearing that efforts to boost hiring were "imperative" for promoting a strong US economic recovery.
MSCI's all-country world stock index rose 0.62%. The pan-European FTSEurofirst 300 index of leading regional shares gained 0.28% to close at 1,297.85.
Japanese equities, made cheap for foreign investors by a falling yen, led the charge, jumping 1.95% to bring gains for the week to a heady 7.65%, the Nikkei index's biggest weekly rise since December 2009.
In commodity markets, Brent crude rose above $108 a barrel, headed for its biggest weekly gain since late August on expectations the Fed would stick with its easy money policy.
Brent crude for January delivery, in its first day as the new front-month, ended 22 cents higher at $108.50 a barrel, after trading as high as $108.65. The contract ended with a 3.2% rise on the week, the biggest weekly gain since July 5.
US crude ended up 9 cents at $93.84 a barrel after trading up to $94.55. But it ended with its sixth straight week of losses as supplies remain high.
