LARGEST POPULATIONS BY COUNTRY

The 16 countries with the largest total population:
Rank	Country / Territory	Population	Date	% of world population	Source
1	Peoples Republic of China[38]	1,338,130,000	June 17, 2010	19.6%	Chinese Official Population Clock
2	India	1,182,040,000	June 17, 2010	17.31%	Indian Official Population Clock
3	United States	309,519,000	June 17, 2010	4.53%	United States Official Population Clock
4	Indonesia	231,369,500		3.39%	Statistics Indonesia
5	Brazil	193,066,000	June 17, 2010	2.83%	Brazilian Official Population Clock
6	Pakistan	169,775,500	June 17, 2010	2.49%	Official Pakistani Population clock
7	Bangladesh	162,221,000	2009	2.38%	UN estimate
8	Nigeria	154,729,000		2.27%	UN estimate
9	Russia	141,927,297	January 1, 2010	2.08%	Federal State Statistics Service of Russia
10	Japan	127,530,000	December 1, 2009	1.87%	Official Japan Statistics Bureau
11	Mexico	107,550,697		1.58%	INEGI estimate National Population Statistics of Mexico[39]
12	Philippines	92,226,600	Mid-2009	1.35%	National Statistics Office medium projection
13	Vietnam	85,789,573	April 1, 2009	1.26%	Preliminary 2009 census results
14	Germany	81,882,342	March 31, 2009	1.2%	Federal Statistical Office
15	Ethiopia	79,221,000	July 2008	1.16%	Ethiopia Central Statistics Agency
16	Egypt	78,383,000	June 17, 2010	1.15%	Official Egyptian Population clock

Approximately 4.54 billion people live in these sixteen countries, representing roughly two-thirds (66.7%) of the world's population as of February 2009.

HISTORY- WORLD POPULATION

Ancient & Middle Ages

A dramatic population bottleneck is theorized for the period around 70,000 BCE. After this time and until the development of agriculture, it is estimated that the world population stabilized at about one million people whose subsistence entailed hunting and foraging, a lifestyle that by its nature ensured a low population density. It is estimated that more than 55 million people lived in the combined eastern and western Roman Empire (CE 300–400).

The Plague of Justinian caused Europe's population to drop by around 50% between 541 and the 700s. The population of Europe was more than 70 million in 1340. The Black Death pandemic in the 14th century may have reduced the world's population from an estimated 450 million to between 350 and 375 million in 1400. It took roughly 200 years for Europe's population to regain its 1340 level.

At the founding of the Ming dynasty in 1368, China's population was reported to be close to 60 million, and toward the end of the dynasty in 1644 it might have approached 150 million. England's population reached an estimated 5.6 million in 1650, up from an estimated 2.6 million in 1500. New crops that had come to Asia and Europe from the Americas via the Spanish colonizers in the 16th century contributed to the population growth. Since being introduced by Portuguese traders in the 16th century, maize and manioc have replaced traditional African crops as the continent’s most important staple food crops. Alfred W. Crosby speculated that increased production of maize, manioc, and other American crops "...enabled the slave traders [who] drew many, perhaps most, of their cargoes from the rain forest areas, precisely those areas where American crops enabled heavier settlement than before."

The population of the Americas in 1500 may have been between 50 and 100 million. Encounters between European explorers and populations in the rest of the world often introduced local epidemics of extraordinary virulence. Archaeological evidence indicates that the death of around 90% of the Native American population of the New World was caused by Old World diseases such as smallpox, measles, and influenza. Over the centuries, the Europeans had developed high degrees of immunity to these diseases, while the indigenous peoples had no such immunity.

Modern era

Urban areas with at least one million inhabitants in 2006. 3% of the world's population lived in cities in 1800, rising to 47% at the end of the twentieth century.

During the Agricultural and Industrial Revolutions, the life expectancy of children increased dramatically. The percentage of the children born in London who died before the age of five decreased from 74.5% in 1730-1749 to 31.8% in 1810-1829. Europe’s population doubled during the 18th century, from roughly one hundred million to almost two hundred million, and doubled again during the 19th century.

       The population growth became more rapid after the introduction of compulsory vaccination and improvements in medicine and sanitation. As living conditions and health care improved during the 19th century, the United Kingdom's population doubled every fifty years. By 1801 the population of England had grown to 8.3 million, and by 1901 had grown to 30.5 million.

      The population of the Indian subcontinent, which stood at about 125 million in 1750, had reached 389 million by 1941. Today, the region is home to 1.5 billion people. The total number of inhabitants of Java increased from about five million in 1815 to more than 130 million in the early 21st century. Mexico's population has grown from 13.6 million in 1900 to about 112 million in 2009. In eighty years, Kenya's population has grown from 2.9 million to thirty-seven million.

MILESTONES BY THE BILLIONS

World population estimates milestones
Population (in billions)	1		2		3		4		5		6		7		8		9		10
Year	1804		1927		1960		1974		1987		1999		2011		2025		2040		2061
Years elapsed		123		33		14		13		12		12		14		15		21

The population of the world reached one billion in 1804, two billion in 1927, three billion in 1960, four billion in 1974, five billion in 1987, and six billion in 1999. The population of the world is projected to reach seven billion in 2011 or 2012, eight billion in 2025, nine billion in 2040, and ten billion in 2061.

There is no estimation on the exact day or month the world's population surpassed both the one and two billion marks. The days of three and four billion were not officially celebrated, but the International Database of the United States Census Bureau places them in July 1959 and April 1974.

        The United Nations did determine, and celebrate, the "Day of 5 Billion" (11 July 1987), and the "Day of 6 Billion" (12 October 1999). The International Programs division of the United States Census Bureau estimated that the world reached six billion on 21 April 1999 (several months earlier than the official United Nations day). The "Day of 7 Billion" has been targeted by the United States Census Bureau to be in July 2012, while the Population Division of the United Nations suggests some time in late 2011.