Large-cap financials beat large-cap information technology for both November and December, which is significant because they are the two largest sectors within the S&P 500.

The outperformance of the large-cap financials is the seventh time since August 2013, said Jodie Gunzberg, managing director, head of U.S. equities at New York-based S&P Dow Jones Indices. This trend is critical because large-cap financials make up 14.8% of the S&P 500 index and the large cap IT stocks consist of 23.8% of the benchmark index.

"In the S&P 500, the financials sector beat information technology in November and December by 2.4% and 2.0%," she said. "This was the first two consecutive months in a year."

The financial sector rarely outperforms the tech sector month-to-month and it has only occurred seven times since August of 2013, which is a total of 53 months, Gunzberg said. In the seven months before August 2013, the financial sector surpassed tech in every month when the U.S. economy was relatively strong compared to international markets.

"When this happens, generally financials outperform information technology since proportionally greater revenue comes from overseas in IT," she said. "There is over 40% weighting in information technology versus just 6.5% in financials inside the S&P 500 Foreign Revenue Exposure Index while the market cap weighted result in the S&P 500 is about 24% in IT and 15% in financials."

The financial stocks could be outperforming due to two critical factors -- the new tax plan and the potential interest rate hikes in 2018, Gunzberg said.

The financial sector is an important part of the rally in 2018, said JJ Kinahan, chief market strategist at TD Ameritrade, an Omaha, Neb.-based brokerage, who agrees with the sentiment that these stocks benefit the most from rising interest rates and the tax cuts.

The tech sector remains interesting for investors and many of the stocks could get a "shot in the arm as a result of increased infrastructure spending on technology across the public and private sectors," he said. "That said, they will have to continue to rely on the continuing good health of economies in the U.S., Europe and Asia, so we'll have to watch to see how it plays out."

The tech sector appears to be reversing the trend so far this month, with the "most S&P 500 market optimism since November 2016," said Gunzberg.

"While positioning inside sectors can help in a potential turn of performance, sticking with large caps on a broader scale may be most beneficial since information technology has lost least on its way down and financials have gained most on the rise across sectors," she said.

If the financial stocks rise, the diversified financials industry group consistently has the highest average monthly returns, Gunzberg said.

"The diversified financials industry group gains more than the sector across every market cap, including large cap, mid-cap and small cap from the S&P 500," she said.

For investors interested in the tech sector, the correlation of technology hardware and equipment industry group remains very high to IT, despite the direction of the returns.

"Semiconductors and semiconductor equipment have significant correlation drops when the performance is split into positive and negative IT months and has a low beta, especially in large and mid-caps when the market is down," Gunzberg said.

The money flows demonstrate that more investors are taking a passive approach to investing and relying on index-based products to invest for their retirement, said Kinahan.

"The popularity of robo-investing has increased and whether because of wage increases or because there are more jobs being created, more people are putting more money into 401(k) plans, which tend to offer index-based funds as part of their line ups," he said. "We would expect this trend to continue for as long as this market rally continues -- historically, after selloffs, there tends to be a shift in investors' outlooks toward investing and the markets."