Brazil - 203 million

40% of Brazil’s land mass is covered by the Amazon rainforest, one of the most inhospitable eco-systems on Earth. It is perhaps surprising then that the country’s population has multiplied 50 times in the last two centuries.

Brazil is so large that despite the fact that only 7% of its land is Arable, it still has the fifth most arable land of any country on earth.

The abundance of farmland meant that colonisers took advantage of the ability to grow vast quantities of exportable goods, largely at the expense of the 50 million enslaved people it brought to the country via the Trans-Atlantic slave trade.

The outlawing of slavery and the subsequent workforce gaps that brought, meant that the country was forced to launch large immigration drives to entice foreign labour to the country to work the land and sustain the economy throughout the late 19^th and early 20^th century.

This combined with a birth rate of around 6 children per woman in the 1970s has contributed to Brazil’s mammoth population.

Nigeria - 223 million

Nigeria is actually one ninth the size of Brazil in terms of land mass but has a staggering 20 million more people.

Despite the fact that 63% of people live in extreme poverty, the custom of teenage marriage is believed to be one of the factors responsible for large fertility rates in a country with GDP comparable with Denmark, a country of just over 5 million people.

43% of women in the country marry before the age of 18, with 16% doing so before the age of 15, meaning that the average fertility rate per woman in the country is 5.3 births, the seventh highest of any country on earth.

With many Muslim communities in the north practising polygamous marriage, where a man can have up to four wives and only 5% of the country using contraception, some of the countries rural areas have fertility rates of 8 babies per woman.

This combined with medical improvements which have reduced child mortality in 30 years has led to an explosion in the Nigerian population in recent years.

Pakistan - 241 million

Despite 60% of the country being desert and mountains, the remaining 40% is some the best agricultural land on earth.

As many urban areas across the world see falling fertility rates, 65% of Pakistan’s population still live in rural areas, where historically, an emphasis on more children means that more make it through to adulthood and are able to support the family and work the land in later life.

The government has attempted to introduce measures to control population increases by improving education, in the hope that research suggesting that there is a correlation between education and fewer children is true.

But a significant amount of the population still do not have a traditional education and this coupled with negligible contraception use means that fertility rates in the country continue to rise.

Indonesia - 279 million

Consisting of 18,000 islands, Indonesia has a land mass slightly bigger than Alaska.

Its tropical climate and rainfall patterns combined with its 45 active volcanoes which produce some of the richest soil on earth means that Indonesian island of Java is perfect for the cultivation of crops to be exported around the globe.

Since being colonised by the Dutch in the 1600s, the island has been one of the world’s foremost producers of coffee, tea, palm oil, rubber and spices ever since, leading to an increase in the amount of people living there to work the land.

The development of sprawling urban centres as the island adapts to global markets has seen he fertility rate fall dramatically in recent years, meaning that it may no longer be in the top 7 in twenty to forty years time.

USA - 334 million

In 1815, the US embraced being the nation of immigrants as it welcomed people from all over the world, brought to the country in the hope of living “the American dream”.

Economic prosperity since World War Two has seen the country flourish with returning soldiers increasing women’s fertility rates to around 3 babies per woman in the post war years.

Advancements in medical care which have seen people live longer combined with a steady influx of immigration, has seen populations steadily rise in recent decades.