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World population is presently about seven billion people. That is a carefully done estimate by professional demographers so let us accept that as being accurate to within ten percent. There is no use asking for a more precise number even at present, and when estimating historical numbers an accuracy of half to double a given number may be overly optimistic.

What is proposed here is a an easy way to remember historical populations. This method is accurate enough to stay historically oriented to population. There are more precise numbers but they should be taken with caution especially when reflecting sudden changes, such as the plague of 1347, where the accuracy is even more suspect. Sometimes data presented will show mathematical precision which isn’t really there. For example, say there are about one hundred thousand people living in a city and about one third of them died in the plague. The quick and easy calculation, commonly seen will do something silly like: a town with a population of 100,000 is struck by plague which is reported to have killed a third of the people. So a precise calculation can be made by dividing the population by 3 which equals 33,333 died leaving a population of 66,667 living people. This is precise enough mathematically but is obvious nonsense in fact. The problem is that a precise number is used for the calculation which gives an exact number when others see this number they think it is accurate to the number stated and they use it to calculate other things. Thus, we sometimes see things which are treated as accurate but when checked into the data was soft and intended for general conclusions and thus any precision is totally suspect. Here is a wonderful site World Population Since Creation which plays lots of mathematical games, some of which are good some of which are “hopefully” intentionally hilarious.

Hoping not to fall into total nonsense there is presented below some reasonable estimates of world population. As you look over the chart notice how widely divergent these professional estimates are. In an effort to cut through the confusion I have been using a simple estimate to keep things in perspective. It isn’t intended to be precisely accurate but it is usually within the error ranges of professional demographers, and it has the advantage of being very easy to learn and to remember. Look over the chart and then look at my method below.

Historical Estimates of World Population

(Population in millions as estimated by professional demographers. When lower and upper estimates are the same they are shown under their name which means “Lower.” For a more complete rendition of this chart a click through is at the bottom.)

Year Lower Average Upper Biraben Durand Upper Haub McEvedy Thom Upper UN, 1999
11,775 BC 15
10000 BC 1 10 4 1 10
8000 BC 5 5
6500 BC 5 10
5000 BC 5 20 5 5 20
4375 BC 30
4000 BC 7 7
3000 BC 14 14
2000 BC 27 27
1175 BC 60
1000 BC 50 50
500 BC 100 100
400 BC 162 162
200 BC 150 231 231 150
1 AD 170 400 255 270 330 300 170 200 300
1 AD 200
200 AD 190 256 256 190
400 AD 190 206 206 190
425 AD 125
500 AD 190 206 206 190
600 AD 200 206 206 200
700 AD 207 210 207 210
800 AD 220 224 224 220
900 AD 226 240 226 240
1000 AD 254 345 254 275 345 265 310
1100 AD 301 320 301 320
1200 AD 360 450 400 450 360
1225 AD 250
1250 AD 400 416 416 400
1300 AD 360 432 432 360 400
1340 AD 443 443
1400 AD 350 374 374 350
1500 AD 425 540 460 440 540 425 500
1600 AD 545 579 579 545
1625 AD 500
1650 AD 470 545 500 545 500
1700 AD 600 679 679 610 600
1750 AD 629 961 770 735 805 795 720 700 790
1800 AD 813 1,125 954 900 900 980
1825 AD 1,000
1850 AD 1,128 1,402 1,241 1,265 1,200 1,200 1,260
1900 AD 1,550 1,762 1,633 1,650 1,710 1,656 1,625 1,600 1,650
1910 AD 1,750 1,750
1920 AD 1,860 1,860
1925 AD 2,000
1930 AD 2,070 2,070
1940 AD 2,300 2,300
1950 AD 2,400 2,557 2,527 2,516 2,500 2,400 2,520
1975 AD 4,000
2026 AD 8,000

Sources: US Census Bureau Historical Estimates of World Population

This graph has my estimates inserted in bold type using a generalized formula, see below. This method is intended as a quick way of remembering approximate populations over the entire human historical period. The bolded data is not too distant from the population experts boundries for maximum and minimum for three thousand years. There may be authorities which would include any specific population estimated for a specified date. The formula requires only knowing that world population was near four billion in 1975 AD and 200 million at 1 AD. Going forward or backward from 1975 the population is doubles in fifty years by doubles, thus going back doubling the amount of years halves the population and that procedure is followed throughout the chart which included as bolded data above. The method gives a good guess back to 1,000 BC which may be as accurate as the population data permits. But it is easy to shift method slightly at 1AD with 200 million people and modifying the halving time at starting to 500 years rather than 50 as from 1975 that adjustment gives a fair estimate all the way back to the advent of agriculture. This concept is hard to describe but is easier to understand if you look over the list below. Set the boundary for these guess at +/- 20% or more.

2025 AD = 8 billion ( this added 50 years to to 1975 to double)

1975 AD = 4 billion remember this date and population ½ in -50 years =…

1925 AD = 2 billion (½ in -100years =…

1825 AD = 1 billion (½ in -200years =…

1625 AD = ½ billion (½ in -400years =…

1225 AD = ¼ billion (½ in -800 years =…

425 AD = 125 million

Shift the method a bit to 500 year for halving

1 AD = 200 million – remember this date and population (½ in -500 years =…

500 BC =100 million (½ in -500 years =…

1000 BC = 50 million (½ in -1,000 years =…

2000 BC – 25 million (½ in -2,000 years =…

4000 BC = 10 million (½ in -4,000 years =…

8000 BC = 5 million (½ in -8,000 years =…

16000 BC = 2.5 million

A good guess has a working central point with upper and lower boundaries.

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