Kensho Stats

Here's what could keep the Dow below 20,000 through the end of the year

Crafworkers with loopes compare blown-up sections of counterfeit hundred-dollar bills with a sample legitimate bill expanded 400 times larger than the real size
Kazuhiro Nogi | AFP | Getty Images

Over the long term, a strong dollar is not bad for the stock market. In fact, studies show it's generally a positive trend over many years. But in the short term, moves higher in the greenback can be jarring as traders focus on the immediate impact to multinationals' exports and other negative effects.

The euro-USD fell to $1.04 on Thursday, 4 cents shy of parity. If it falls to parity before the end of 2016, it could spell trouble for investors hoping for a Santa Claus rally that takes the Dow Jones industrial average above 20,000, history shows.

Using Kensho, we looked at what happened to the Dow whenever the euro fell 4 cents in two weeks vs. the U.S. dollar. This occurred 42 times in the last decade:

The Dow posts an average decline of 1.6 percent and was only positive during 40 percent of those two-week periods. The big global exporters lead the drop.

Disclosure: NBCUniversal, parent of CNBC, is a minority investor in Kensho.