Video: Decoding the middle class

BOSTON — America's middle class is in trouble, a development that is producing serious consequences for the lives of millions of people.

It's also affecting the well-being of the US economy.

Around the developing world, however, the story is very different.

Over the past two decades — and roughly during the same time as the middle class has struggled in the US — millions of people have moved out of poverty and into middle class status.

The trend is complex, but it has profound implications for life in the world's largest economy, as well as for people across the globe.

Here's the issue, decoded in three questions: