NEW YORK — The last time the stock market had this long a winning streak, Twitter shares weren’t even a part of it yet.

Yet another gain for stocks on Thursday sent the Standard & Poor’s 500 index higher for an eighth straight day, its longest winning streak since July 2013, which was months before Twitter shares started trading publicly. It’s the latest step higher for a market that has methodically climbed to record after record for much of this year as both the economy and corporate profits have improved.

The S&P 500 rose 14.33 points, or 0.6 percent, to 2,552.07. The Dow Jones industrial average gained 113.75, or 0.5 percent, to 22,775.39, and the Nasdaq composite rose 50.73, or 0.8 percent, to 6,585.36. All three indexes added to their records set a day earlier, again.

All those moves higher actually have some professional investors a bit nervous, because even the healthiest markets tend to have some sharp sell-offs from time to time. The last time the S&P 500 had a pullback of just 5 percent was more than a year ago.

“What’s really troubling most people more than anything is that we just go straight up,” said J.J. Kinahan, chief strategist at TD Ameritrade. “There hasn’t been a pullback. That’s what most on Wall Street are trying to come to grips with.”

Encouraging reports on the economy have been helping stocks, and on Thursday they included a stronger-than-expected rebound in U.S. factory orders during August and a drop in the number of workers applying for unemployment benefits last week.

Friday’s report from the Labor Department on monthly job growth will likely show momentum in the opposite direction, with most economists forecasting a drop-off in hiring. But that’s mostly because of damage caused by recent hurricanes, which hopefully will be only temporary.

With the economy and corporate earnings seemingly solid, TD Ameritrade’s Kinahan said if there is a trigger for a downturn in stocks, it would likely be either a new flash in political tensions with North Korea or somewhere else in the world, or a stumble in Washington’s progress to reform the tax system.

Netflix jumped to the biggest gain in the S&P 500 on Thursday after it raised the price on its most popular U.S. video streaming plan by 10 percent. Shares rose $9.94, or 5.4 percent, to $194.39.

Constellation Brands was close behind after it reported stronger earnings for the latest quarter and raised its forecast for upcoming profit. The company has been focusing on the higher end of the beer, wine and spirits markets. Its stock rose $8.07, or 4 percent, to $209.25.

On the losing end was student-loan servicing company Navient, which fell $2.09, or 14.3 percent, to $12.61. It said it was buying Earnest, a lender, for $155 million and would suspend its stock buyback program through 2018. Pennsylvania’s attorney general also alleged in a lawsuit filed Thursday that Navient improperly added billions of dollars in costs to borrowers.

The yield on the 10-year Treasury note climbed to 2.34 percent from 2.32 percent late Wednesday. Higher interest rates tend to help financial stocks on the expectation that banks will make bigger profits from lending, and financials in the S&P 500 rose 1 percent.

Stock markets overseas were generally quiet, as exchanges in several of Asia’s biggest exchanges were closed for holidays. Japan’s Nikkei 225 index was virtually flat, France’s CAC 40 rose 0.3 percent, Germany’s DAX was close to flat and the FTSE 100 in London rose 0.5 percent.

The dollar fell to 112.85 Japanese yen from 112.98 yen late Wednesday. The euro dipped to $1.1708 from $1.1764, and the British pound slipped to $1.3116 from $1.3250.

In the commodities markets, benchmark U.S. crude rose 81 cents, or 1.6 percent, to settle at $50.79 per barrel. Brent crude, the standard for international oil prices, rose $1.20 to $57 per barrel.

In other energy trading, heating oil rose 1 cent to $1.79 a gallon, wholesale gasoline rose 3 cents to $1.61 a gallon, and natural gas fell 2 cents to $2.92 per 1,000 cubic feet.

The price of gold fell $3.60 to $1,273.20 an ounce, silver edged up 1 cent to $16.64 an ounce, and copper jumped 9 cents to $3.05 a pound.