The median household income of a Trump voter so far in the primaries is about $72,000, based on estimates derived from exit polls and Census Bureau data. That's lower than the $91,000 median for Kasich voters. But it's well above the national median household income of about $56,000. It's also higher than the median income for Hillary Clinton and Bernie Sanders supporters, which is around $61,000 for both.

There's a chart of 23 states, and only in Vermont do Clinton supporters have a much higher income than Trump supporters. Clinton is slightly higher in Connecticut and Virginia, and in every other state Trump supporters are making more money than Clinton supporters. Bernie Sanders supporters are richer than Ted Cruz supporters in New York, but in every other state Sanders has poorer supporters than all three Republicans.

This is the key sentence in the article: "Class in America is a complicated concept, and it may be that Trump supporters see themselves as having been left behind in other respects."

My explanation goes back to the deepest problem of being human: the need for life to feel meaningful. This is a book-length subject, so I'll skip ahead to the modern age and say that, in humanity's search for meaning, economic growth was a temporary hack: for a brief time, ordinary people could be part of a great story in which almost everyone was getting more prosperous.

If you've played video games, you know that almost all of them are built around some kind of improvement, and it would be hard to make a compelling game in which nothing is getting better. But that's where we are now as a society. Trump supporters don't have to be poor to feel like they're missing out -- they just have to not be getting richer. But almost nobody is getting richer, so how does this translate into different political factions?

Sanders supporters want to make the poor richer by making the rich poorer. The establishments of both parties refuse to accept that the age of economic growth is over. And the Republican fringe, which is now taking over the party, has given up on economics and gone back to tribalism. Nate Silver agrees: in his analysis of Why Republican Voters Decided On Trump, his number one reason for why he was wrong about Trump is "Voters are more tribal than I thought."

He never explains this, but I'll try. My off-the-cuff definition of "tribalism" is the habit of generating meaning by dividing the world into the in-group and the out-group. Liberals do this too, we all do it a little, and I'm not going to excuse it. It's a mistake and something that humanity has to overcome. But in the short term it's going to get much worse as it expands to fill the void left by the end of economic growth.

Other things are also expanding to fill this void, like prescription opioid addiction and the desire to colonize Mars. I have at least two horses in this race. One is conscientious hedonism, letting go of achievement and having a good time in ways that don't lead to having a bad time later. The other is to find meaning in downsizing.