In Pharyngula article Humanity’s recent surge, PZ discusses a chart from The Economist. The chart deals with population and growth rate on the same time scale by century.
The article got me wondering how the data would look if you plotted it along a population weighted year (PWYr) time scale.
(NOTE: this idea seems quite simple and obvious, so I suspect someone has done this before, but I could not find it.).
(NOTE: this idea seems quite simple and obvious, so I suspect someone has done this before, but I could not find it.).
So what is a PWYr?
A PWYr is a measure of time based on the number of years lived collectively by a population over some long time scale (i.e. where population is changing dramatically). It turns out that a PWYr is equal average population over a reference period. A table of PWYr shift the years such that it creates a corresponding date within the reference period that assumes a constant population over that period.
A PWYr is a measure of time based on the number of years lived collectively by a population over some long time scale (i.e. where population is changing dramatically). It turns out that a PWYr is equal average population over a reference period. A table of PWYr shift the years such that it creates a corresponding date within the reference period that assumes a constant population over that period.
So whats good about it?
The interesting thing is that change especially for technology, knowledge, and research driven endeavors like economics, science, longevity, communication, etc. should be at least in part proportional to the number of people living. In other words, for any society, the more people there are, the more that can contribute to change, and so the faster the change appears. I came up with the notion of a PWYr a few years ago and always thought it would be an interesting way to watch change over the centuries.
So what does it look like?
To see what a Population Weighted Year looks like, I used World population data from Wikipedia to calculate roughly how many years lived over each of the population intervals. I then summed the total years lived and divided by the total period covered to get the average population, which is also the number of years lived in a population weighted year. When I took the period from 0 CE to 2010, I get:
So what does it look like?
To see what a Population Weighted Year looks like, I used World population data from Wikipedia to calculate roughly how many years lived over each of the population intervals. I then summed the total years lived and divided by the total period covered to get the average population, which is also the number of years lived in a population weighted year. When I took the period from 0 CE to 2010, I get:
1 PWYr (0-2010) = 603,902 years lived
From there is is simple to calculate the equivalent date in PWYrs for each interval which I have calculated in Table 1. You may ask Why 0 to 2010? I was trying to look at the time line from roughly to day and so 2010 was the closest date to today.
Table 1: Calendar year vs Population weighted Year (PWYr) based on the average population (603902890) from year 0 to 2010. Therefore, 1 PWYr is equivalent to 603,902,890 years lived by the world population. The data came from Wikipedia World Population Estimates article.
Year
|
Estimate Population*
|
Population Weighted Year (PWYr)
|
-8000
|
5000000**
|
-2020
|
0
|
300000000
|
0
|
1000
|
310000000
|
505
|
1250
|
400000000
|
652
|
1500
|
500000000
|
838
|
1800
|
978000000
|
1179
|
1850
|
1262000000
|
1271
|
1900
|
1650000000
|
1392
|
1930
|
2070000000
|
1483
|
1950
|
2529346000
|
1559
|
1960
|
3023358000
|
1605
|
1970
|
3685777000
|
1660
|
1980
|
4437609000
|
1727
|
1990
|
5290452000
|
1808
|
2000
|
6115367000
|
1902
|
2010
|
6908688000
|
2010
|
*UN Department of Economic and Social Affairs (2008)
**Population for 8000 BCE is from Population Reference Bureau (1973–2008)
