The United Nations Population Division (UNPD) publishes their Population Prospect report every couple of years. The most recent report was revised in 2012 and released in June, 2013. At that time (mid 2013) they projected the world's population to be between 7.13 and 7.2 billion. The medium projection is 7.16 billion with an annual rise of about 82 million (about 156 per minute). According to their data, by 2015 the world will reach a population of 7.28 billion souls and by 2050 it could reach 9.5 billion.

Estimates are based on reports (an application form) from each country. From these reports the UNPD demographers weigh census age, accuracy, and many other factors in adjusting their 2010 population estimates. They then calculate future population projections based on assumptions of fertility, income, education, health, and other social factors. Because these factors can not be predicted with certainty, the UNPD provides a high, medium, and low projection.

The U.S. Census Bureau uses their own sources, demographers, and formulas. Their world population projection is considerably more conservative than that of the United Nations. Mid 2013 they calculated the world population at 7.1 billion. By 2015 the US census bureau projects that world population will rise to 7.22 billion, nearly 2 years behind the UN projections.

* At we have elected to use the United Nations medium projection for all population calculations, except where noted. Death rates, too, are calculated from UNPD reports. Compare this with the similar (but not identical) world death rate on the Mortality pages where the World Health Organization projections are used. Although we could have interpolated the data to make one agree with the other (essentially fudging the numbers), we chose, instead, to leave this disparity and keep source accuracy.

SOURCES: " + 'UN Population Division | US Census Bureau