NEW YORK (Reuters) - The dollar has moved from a supporting role to a featured player this earnings season, a boon to U.S. multinationals which have benefited from the biggest quarterly year-on-year decline in the greenback in three years.

Traders work on the floor of the New York Stock Exchange (NYSE) in New York City, New York, U.S., October 27, 2017. REUTERS/Brendan McDermid

Since the start of October, at least 35 U.S. companies have cited currency “benefits” or “tailwinds” and “weaker dollar” for boosting quarterly earnings, compared with few mentions a year ago, and some see that extending to the fourth quarter, a Reuters analysis shows.

“The quarter was one where the dollar weakened over the course of the quarter, more so than analysts expected,” said Jill Carey Hall, equity and quantitative strategist at Bank of America Merrill Lynch in New York.

“That’s what’s in part been helping multinationals,” Carey Hall said. “They have seen some of the strongest results so far.”

The U.S. dollar index's .DXY average in the third quarter fell from its year-ago level by about 2.5 percent, the weakest showing since 2014, Thomson Reuters data shows.

The index has recovered from its recent lows, but remains down about 7 percent for the year.

U.S.-based multinational companies can benefit the most from declines in the dollar, which make overseas sales more valuable when translated back into the U.S. currency.

Among companies citing a positive dollar impact were Alphabet Inc GOOGL.O, International Business Machines Corp IBM.N and other names in technology, which has the highest percentage of foreign sales within the S&P 500.

Others included Axalta Coating Systems Ltd AXTA.N, W.R. Grace GRA.N, Coca Cola Co KO.N and Xerox Corp XRX.N, which said the third quarter was the first in 13 that a weaker dollar boosted the company's earnings, by about 1 percentage point.

“And we’re expecting that to improve into Q4 based upon quarter-end rates,” Xerox Chief Financial Officer William Osbourn said in the company’s Oct. 26 conference call after it reported higher-than-expected results.

The weaker dollar "should help with the discounting pressure from the non-U.S. manufacturers, so that's a good sign," Harley-Davidson HOG.N Chief Executive Matthew Levatich told investors Oct. 17.

The dollar’s weakness has helped offset the impact of a trio of hurricanes that took a heavy toll on companies in the third quarter. If the benefit continues, it could help companies hit the 11.7 percent profit gains analysts have projected for the fourth quarter.

With results in from more than three-quarters of the S&P 500 companies, third-quarter profit growth is estimated at 8.0 percent, up from 4.3 percent three weeks ago, Thomson Reuters data shows.

Much of the improvement has come with stronger-than-expected technology results. Ninety percent of S&P technology index .SPLRCT names are beating earnings expectations, while 72 percent are surpassing estimates in the overall S&P 500, the data shows.

Materials companies’ earnings, which have benefited from higher commodity prices tied to the weaker dollar, have had a high percentage of beats as well.

Adding to the weaker dollar’s benefit has been better global economic strength, and that is also why multinational companies have performed better than others this earnings season, Carey Hall said.

S&P 500 companies with 50 percent or more of sales coming from outside the United States have estimated profit growth of 16.7 percent for the third quarter, compared with 5.5 percent for companies with less than 50 percent of non-U.S. sales, Thomson Reuters data shows.

Stocks of big multinationals also have outperformed, with the Dow Jones global titans index .DJGT up about 3.3 percent since Oct. 1. The small-cap Russell 2000 index .RUT is up just 0.2 percent since then.

“It’s not so much the dollar is a windfall for them; it’s no longer a headwind, so that’s positive, and outlooks for companies have been generally upbeat,” said David Katz, chief investment officer at Matrix Asset Advisors in New York.