The global life expectancy is currently in the low 60s, around 63 or 64. Of course, the life expectancy in the developed world is usually in the high 70s and in the developing world it can be closer to 50 or even 40, and this imbalance is one of the great social ills of our times; however, it is worth remembering that in the last one hundred years, life expectancy has soared around the world. In the early twentieth century, the global life expectancy was between 40 and 45.

In Western Europe and North America, the population is basically steady; it is neither climbing nor shrinking dramatically. In Eastern Europe, the population is shrinking. In parts of East Asia, the population is climbing slowly. In Sub-Saharan Africa (as well as South Asia), the population is skyrocketing.

In 2014, Qatar experienced the fastest population growth in the world. The population of Qatar increases by as much as ten percent every year. Qatar is a very small country in the Middle East that has recently undergone a revolutionary growth in economic prosperity. Much of Qatar’s rampant population growth is being driven by immigrants arriving from South Asia in search of work.

Almost every geographer and demographer agrees that over the course of the twenty-first century Africa will witness by far the largest population growth. Some demographers expect the population of the continent to quadruple, from a bit over one billion to more than four billion people. That means there will be three billion more Africans alive in 2100 than were alive in 2000. To put that into context, over the same time period, the combined populations of Asia, North America, and South America are projected to grow by a little less than one billion!

Almost all of the world’s fastest growing countries can be found in Africa. Africa is the least developed continent on Earth, but it is rapidly developing in recent years. Many countries in Africa are experiencing stage 2 of the demographic transition model; where death rates are starting to fall, but birth rates remain steadily high. This leads to massive population growth.

Less developed countries often experience greater population growth because they are in the "infancy stage" of development. In addition, countries with a high birth rate and low mortality rate will have a shorter doubling time because number of births will greatly exceed the number of deaths. 

To undergo a population implosion entails that the population is decreasing, hugely due to a higher death rate than a birth rate. Europe has definitely been going through this for years. The other mentioned others have been more going through populations explosions, with growing populations.