For the first time ever, humans have nowhere new to go. People have filled almost all the space on the planet where they can live.

Yet only a few years ago, there were still big empty countries with plenty of space for newcomers (immigrants or migrants). People were invited to come and start a new life in America or Australia away from crowded Europe. Not any more! Now no countries in the world want more people coming in - unless they have special skills which are needed (like doctors, nurses and teachers). People who want to escape miserable lives and start again can't just migrate to richer countries like before. The rich countries don't want them. This makes big problems in many parts of the world. Poor people from Mexico and other Latin American countries like Guatemala and Colombia want to come to the United States to make a better life for themselves and their families. But only a few are allowed in. The border is sealed by fences and patrolled by guards night and day. Some 'illegals' break through. Some get caught and sent back. And some die trying to make the crossing. The rich countries of Europe have similar difficulties.

The bottom line is there's not enough for everyone to be well-off like most of those people who live in Europe, Australia and North America. Those who have make sure that those who don't aren't allowed in to share some of their wealth. So the poor stay poor and the rich stay rich.