Stocks have given back their premarket gains by the midway mark.

The Dow Jones Industrial Average is down 57 points midday, while the Nasdaq Composite and S&P 500 are also modestly lower, with all three benchmarks looking to extend yesterday's losses.

Here we take a look at the top shorts of each year between 2013 and 2020. The list is based on data from Activist Insight Shorts.