Gerrymandering is the practice of redrawing electoral district boundaries to give one political party an unfair advantage over its opponents. While gerrymandering can have a significant impact on the outcome of local and state elections, simulations have shown that its effects largely cancel each other out on a national scale.

In a study published in the journal "Nature", researchers from the University of Michigan found that gerrymandering has only a small effect on the national popular vote, with Democratic and Republican gerrymanders largely offsetting each other. The study found that the most extreme gerrymanders could affect the national popular vote by no more than 1.5 percentage points, and that the average effect of gerrymandering was less than 0.5 percentage points.

Another study, published in the journal "Electoral Studies", found similar results. The study found that gerrymandering had a larger impact on the partisan composition of the U.S. House of Representatives, but that this impact was still relatively small. The study found that gerrymandering could account for up to 6% of the Republican Party's advantage in the House.

These studies suggest that gerrymandering is a problem that has a real impact on the fairness of elections, but that its effects are limited on a national scale. However, it is important to note that these studies are based on simulations, and the actual effects of gerrymandering may be different in practice.