According to the Worldometer website which publishes population data from a variety of sources, the world population at the end of 2017 has risen by 83.3 million for the year and now stands at 7.6 billion.

The countries with the highest populations in the world are China 1.41 billion, India 1.35 billion and the USA 324 million.

New Zealand's population at the end of 2017 was 125th out of the 233 states in the world; according to Stats NZ the current population is 4.84 million.

There is one birth every 9 minutes in New Zealand, one death every 17 minutes and a net migration gain of one New Zealand resident visa holder every 7 minutes.

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The projection for 2050 is that India will be the most populous country, 1.66 billion, China's population is projected to decrease to 1.36 billion and will be in second place.

The surprise is Nigeria in third place with 411 million. Stats NZ estimate that the New Zealand population will be between 5.28 and 6.58 million in 2043.

Forecasts of the highest population growth and decline rates vary considerably between data sources (the World Bank, the UN, the CIA and the US Census Bureau).

Using several of these sources, Worldometer concludes that the highest yearly change in population are: Oman 4.8%, Bahrain 4.7% followed by a number of Sub-Saharan countries including Niger 3.9%, Equatorial Guinea 3.8%, Angola, DR Congo, Uganda and Burundi.

These percentages are the average annual change in population resulting from a surplus of births over deaths and the balance of migrants entering and leaving the country.

The same data source reveals that the countries with the highest percentage population decline in the world during 2017 were Latvia -1.1%, Pacific islands Wallis and Futuna -1.1%, Syria -0.9%, Croatia, Bermuda and Romania.

Fertility rates per country also reveal some interesting trends.

Fertility rate is defined as the average number of children a woman in that country has in her childbearing years.

The highest in the world are Niger 7.4, Somalia 6.6, Mali 6.4, DR Congo 6.4, Chad, Angola and Burundi. The fertility rate in New Zealand is 2.

Alarmingly, the countries with the highest fertility rates tend to be the poorest and most underdeveloped. Poverty generally means poor education, lack of awareness and access to contraception - children are considered necessary to provide for the family.

The lowest fertility rates in the world are all in SE Asian: Taiwan 1.1, South Korea, Hong Kong and Singapore each 1.2.

Low fertility rates tend to be associated with economies where contraception is easily available, women have good job opportunities and remain in the work force, and where couples are deterred from having many children because of the high costs of living and housing.

Infant mortality rate is defined as the number of deaths per 1,000 live births of children under one year of age.

The CIA Factbook for 2017 shows that the highest infant mortality rates in the world are, Afghanistan 110.6, Mali 94.8 and the Central African Republic 86.3. New Zealand's, according to this database is 4.4 which puts it in 183rd place.

There has been a dramatic increase in the percentage of the population who are 65 years or more.

According to the World Bank, the highest percentages are Japan 27 per cent, Italy 23 per cent and Portugal, Germany and Finland each 21 per cent.

These figures are set to escalate dramatically. In 2050, it is predicted that 37 per cent of the Japanese population will be over 65, South Korea 35 per cent, Spain 34 per cent and Italy 33 per cent. Stats NZ estimates that by 2051 27 per cent of New Zealanders will be over 65, currently it is 14 per cent.

Although the world population is increasing, population growth rate actually declined – from 1.14 per cent in 2016 to 1.12 per cent in 2017, however the problems posed by the trends revealed in all of the population data are potentially severe.

The rapid growth in the number of people over 65 will put a huge cost burden on the working young and the high fertility and population growth rates in the poverty stricken Sub-Saharan countries is prompting mass migration to the wealthier countries.

That will put even more economic, social and political pressure on the countries of the developed world.

https://www.stuff.co.nz/world/100488712/nigeria-predicted-to-become-third-most-populated-country-by-2050