For many people, the idea of a world based on liberty is flawed.  As long as people are free to keep having babies, then eventually we’re going to run out of resources.  At the time of this writing, the population of the world is over 7.2 billion people, and that number is rising fast.  At this rate, the population will grow to 8 billion people by 2030, and 9 billion by the year 2050, according to the United Nations.
However, surprising as it may seem, the overpopulation bomb has been defused.  Why?  Because women in developed countries tend to have fewer kids.

The above graph shows birth rates are falling below two babies per woman, across the developed world.  In the United States, fertility rates are at a record low, at 1.8 children per woman.  A similar phenomenon is happening in the rest of the developed world: women are having less than 2 children.
By contrast, in the undeveloped world, women tend to have more children.  Niger’s average birth rate is a record 7 children per woman, however, this is going down too, as these countries become more developed.  In general, women around the world are having fewer babies.
The solution to the overpopulation bomb then, is prosperity.  And the best way to achieve prosperity is liberty.  According to the Fraser Institute’s Economic Freedom of the World Index, countries with more liberty experience more prosperity, in general.  Countries at the top of the Economic Freedom of the World Index tend to have the lowest birth rates in the world.

 
Aren’t We Running Out of Resources?
Still, some may be worried that a population of 7 billion cannot be sustained indefinitely by the amount of resources available in the world. As resources like oil, timber, and natural gas continue to be used up, surely 7 billion people will not be able to survive forever.
However, as time goes on, resources seem to get more plentiful.  The economist Julian Simon made a famous wager with Paul Ehrlich, betting resources would become more abundant over a ten year period.  Paul Ehrlich wrote in The Population Bomb, that the world would “run out of resources” by the 1980s.  However, Ehrlich lost the bet to Simon, as resources became more available.
Some say Simon was lucky, but many say that he simply understood the price system.  Simon theorized that when prices increase, it sends a signal to suppliers to look for more resources, or alternatives.  This results in more resources than would have been found if the price had not gone up.
Under-population
Doomsayers have often predicted the end of the world.  According to The Population Bomb author Paul Ehrlich, we should have all starved by the 1980s.  However, the invisible hand of Adam Smith has defused the population bomb, to the point where some news papers are beginning to warn of the newest catastrophe, The Underpopulation Bomb.
According to the theory, under-population will result in a stagnant economy.  Perhaps this is true, but it’s important to remember the solution to the last problem.  For if the invisible hand of the free market could defuse a problem as complicated as overpopulation, surely it can solve an under-population crisis as well.