Tune in to any cable news network in the evening hours and chances are that, no matter the topic, you'll be watching a white guy. Our recent study of diversity on 13 evening cable news shows revealed that white men were hosted 58 percent of the time during April 2013. And this is as true today as it was five years ago.

Back in 2008, we conducted a similar study of evening cable news shows for the month of May, and we found nearly identical results.

Ethnic diversity has improved slightly. In May 2008, white people made up 84 percent of all guests, but that has dropped a bit to 79 percent for last month.

By contrast, men saw a small increase in representation -- from 67 percent to 71 percent -- while the proportion of women fell from 33 percent to 29 percent.

Looking at all three networks together obscures the fact that most of the improvement can be attributed to a single channel: MSNBC. But even though MSNBC saw a slight increase in gender diversity, both CNN and Fox News' larger proportions of men between May 2008 and April 2013 still widened the gender gap overall.

And again, the proportion of white men increased on both CNN and Fox: from 55 percent to 62 percent and from 56 percent to 60 percent, respectively. MSNBC instead dropped its proportion of white men from 61 percent to 54 percent, which was still not enough to stop the gap between white men and all other guests from widening overall.

The proportions of non-white guests, though, rose for all three networks. But most of the gains happened on MSNBC, where the proportion of non-white guests increased from 17 percent to 27 percent. By contrast, Fox only increased by 5 points, and CNN only increased by 2 points.

While we see some small improvement in ethnic diversity between these two snapshots nearly five years apart, all three networks still have a long way to go. National discussion on evening cable news shows still remains primarily the domain of whites and men.