traders
Traders work on the floor at the New York Stock Exchange (NYSE) in New York, U.S., July 29, 2019.
  • The Nasdaq has outperformed the S&P 500 to start the year by a significant margin. 
  • But historical data cited by DataTrek Research suggests the tech sector could slip soon. 
  • When the Nasdaq beats the S&P 500 by 5 points or more over 50 days, underperformance has followed.

The Nasdaq has more than doubled the gains of the S&P 500 to start the year, but a key historical pattern suggests there's reason to be cautious on the tech-heavy index moving forward, according to DataTrek Research.