S&P 500 posts 70th record close, Dow rises for sixth straight day

The S&P 500 rose Wednesday, eking out its 70th record close of 2021.

The benchmark index ticked up 0.1% to 4,793.06. The Dow Jones Industrial Average added 90.42 points, or 0.3%, at 36,488.63. The blue-chip average closed at a record for the first time since November and posted its sixth-straight winning day. The Nasdaq Composite bucked the trend and ticked down 0.1% to 15,766.22.

The S&P 500 has closed at a record 28% of the time in 2021. This year has seen the second-highest number of record closes ever, behind 77 closing highs in 1995.

Investors are hoping to end the year on a high note with the S&P 500 returning more than 27% in 2021 and the Dow up more than 19%. The two indexes are both within striking distance of their all-time highs.

Historically, the market rises during the "Santa Claus rally" period — the last five trading days of December and the first two of January.

"The seasonals favor further gains in the market. The trading is a little thinner than it would otherwise be. ... We're coming off what seems to have been a good holiday season and I think that inspired some confidence," said Wells Fargo Investment Institute's Gary Schlossberg.

Biogen surged roughly 9.5% and led the S&P 500 after a report in South Korean media said the biotechnology company is in talks to be acquired by Samsung. The deal would reportedly be worth more than $40 billion. Biogen declined to comment on the report.

Walgreens, Nike and Home Depot were the top gainers on the Dow, each rising more than 1%.

On the downside, travel-related stocks struggled. American Airlines pulled back 2.6% and United Airlines fell 1.9%. Carnival and Norwegian Cruise Line both closed lower. Boeing led decliners on the Dow with a 1.2% pullback.

Higher-growth technology stocks dipped as the benchmark U.S. 10-year Treasury yield jumped above the 1.5% level. Rising rates discount the value of future earnings and therefore can hit growth stocks like technology names particularly hard. AMD lost 3.2%.

Investors continue to monitor developments with the omicron Covid strain.

The U.S. has confirmed more than 4.5 million Covid cases this month, according to data from Johns Hopkins University. That's well above November's tally of 2.54 million. The country's seven-day average of cases is also at 260,133.29 cases, more than 260% higher than the average from Nov. 28.

However, the Centers for Disease Control and Prevention this week shortened its isolation recommendation for people who test positive from 10 days to five if they don't have symptoms. Research from South Africa also suggests that omicron infections can boost immunity against the delta variant.

The market has shown resiliency in the past few weeks as traders weigh the omicron variant and potentially tighter monetary policy from the Federal Reserve next year. The S&P 500 is up roughly 5% for December.

Next year should bring normalizing economic conditions and slowing growth, Destination Wealth Management's Michael Yoshikami told CNBC's "Squawk on the Street."

"There's inevitably going to be a return to some sort of normalcy, although I think volatility will continue," Yoshikami said. "Three headwinds — inflation, what's happening with the pandemic, and, in our view, tax policy ... are going to bring things back down to more reasonable levels."

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