Voters often conclude that the effort needed to cast a ballot is simply not worth it. So, researchers at Northern Illinois University set to find the most US states where it’s hardest to vote.

In the US, states and counties run elections, so state laws change the difficulty of casting a ballot even in nation-wide races. Allowing residents to vote by mail, for example, lowers the cost of voting. Laws that make registration difficult increase the cost. Scot Schraufnagel and his co-authors (pdf) examined 33 different state-level laws over the past six presidential elections to develop a cost-of-voting index. They looked at seven factors: voting convenience, identification requirements, poll hours, registration deadlines, registration restrictions, registration-drive restrictions, and preregistration rules.

Here’s how each state fared.

The relative ease of voting has changed dramatically since 1996, the earliest election the researchers considered. Some of what were once the easiest states to vote in are now the hardest. Some of the hardest are now the easiest.

As the researchers note, if a state decreases in rank, “we can assume that it has either failed to play catch up” as other states made their voting easier, “has gone out of the way to make voting more costly” or has done both.