Who Has Control of the US Government?

I was working on a fun project which involved taking a look at who controlled the House, Senate and Presidency each year for the past 50 years. Since I had the data sitting around, I decided to make a quick graphic of it. You can click on the picture to see a bigger version of it.

My goal was to convey who had control (the majority), but also show that often it's a very narrow majority each year. I'd love to hear your feedback on how to make it better. I'll make sure to share my final project too when it's done.