Nowadays, overpopulation is still a problem for many country, not just because it causes many nuisane problems but it also effects badly to our life.
First of all, there will be shortage of accomodation, it will be no house for everyone, so they have to live in the slums - where can be very dangerous and unconvenient for people.
Second, medical care equipments will not have good quality, and bad healthcare will not help us in this world - where has so many dangerous disease like now.
Lastly, Crime can be a problem. When they need money badly for their poor life, there will be crime. Criminals can be limit, but it won't last for long.

In conclusion, an overcrowded world is a big problem.

It took hundreds of thousands of years for the world population to grow to 1 billion. However, in just another two centuries, it grew sevenfold. You know, in 2011, the total population of the world reached 7 billion. And today, it's about 7.5 billion. Tokyo, with 37.8 million residents, continues to be the largest city in the world in terms of population.

Advances in modern medicine are the main cause of this dramatic growth in the world population. It helps the birth rates increase and the death rates decline. The second contributor is the improvement in living standards. This leads to the rise of global lifespan, from 64.8 years in the early 1990s to 70.0 years today. Last but not least, the number of women of reproductive age is increasing day by day.