Some startling figues here off wiki:
Projections of population growth
According to projections, the world population will continue to grow until at least 2050, with the population reaching 9 billion in 2040, and some predictions putting the population in 2050 as high as 11 billion.
According to the United Nations' World Population Prospects report:
The world population is currently growing by approximately 74 million people per year. Current United Nations predictions estimate that the world population will reach 9.0 billion around 2050, assuming a decrease in average fertility rate from 2.5 down to 2.0.
Almost all growth will take place in the less developed regions, where today's 5.3 billion population of underdeveloped countries is expected to increase to 7.8 billion in 2050. By contrast, the population of the more developed regions will remain mostly unchanged, at 1.2 billion. An exception is the United States population, which is expected to increase 44% from 305 million in 2008 to 439 million in 2050.
In 2000-2005, the average world fertility was 2.65 children per woman, about half the level in 1950-1955 (5 children per woman). In the medium variant, global fertility is projected to decline further to 2.05 children per woman.
During 2005-2050, nine countries are expected to account for half of the world's projected population increase: India, Pakistan, Nigeria, Democratic Republic of the Congo, Bangladesh, Uganda, United States, Ethiopia, and China, listed according to the size of their contribution to population growth. China would be higher still in this list were it not for its One Child Policy.
Global life expectancy at birth, which is estimated to have risen from 46 years in 1950-1955 to 65 years in 2000-2005, is expected to keep rising to reach 75 years in 2045-2050. In the more developed regions, the projected increase is from 75 years today to 82 years by mid-century. Among the least developed countries, where life expectancy today is just under 50 years, it is expected to be 66 years in 2045-2050.
The population of 51 countries or areas, including Germany, Italy, Japan and most of the successor States of the former Soviet Union, is expected to be lower in 2050 than in 2005.
During 2005-2050, the net number of international migrants to more developed regions is projected to be 98 million. Because deaths are projected to exceed births in the more developed regions by 73 million during 2005-2050, population growth in those regions will largely be due to international migration.
In 2000-2005, net migration in 28 countries either prevented population decline or doubled at least the contribution of natural increase (births minus deaths) to population growth. These countries include Austria, Canada, Croatia, Denmark, Germany, Italy, Portugal, Qatar, Singapore, Spain, Sweden, United Arab Emirates and United Kingdom.
Birth rates are now falling in a small percentage of developing countries, while the actual populations in many developed countries would fall without immigration.
By 2050 (Medium variant), India will have 1.6 billion people, China 1.4 billion, United States 439 million, Pakistan 309 million, Indonesia 280 million, Nigeria 259 million, Bangladesh 258 million, Brazil 245 million, Democratic Republic of the Congo 189 million, Ethiopia 185 million, Philippines 141 million, Mexico 132 million, Egypt 125 million, Vietnam 120 million, Russia 109 million, Japan 103 million, Iran 100 million, Turkey 99 million, Uganda 93 million, Tanzania 85 million, Kenya 85 million and United Kingdom 80 million.
2050
Africa - 1.9 billion
Asia - 5.2 billion
Europe - 674 million
Latin America & Caribbean - 765 million
North America - 448 million