overcrowded traffic in taiwan at rush hourREUTERS/Nicky Loh
The human population is growing at an alarming rate. By 2050, there will be almost 10 billion people on the planet. 
We've been hearing this for years, but where is the most growth happening? 
Today, Tokyo is the most populous city in the world, with about 38 million residents.
Currently, just one of the 10 most populous cities in the world is in Africa (Cairo), and only two (Sao Paulo and Mexico City) are in Latin America. But in the next three decades, that's going to change. 
Based on population growth models, the Global Cities Institute at the University of Toronto projects these will be the 10 biggest cities in 2050.