Person Year

References

https://en.wiktionary.org/wiki/man-year#Noun
- QUOTE: One person's working time for a year, or the equivalent, used as a measure of how much work or labor is required or consumed to perform some task.

http://evonomics.com/how-10000-years-of-war-made-humans-the-greatest-cooperators/
- QUOTE: Turchin estimates that the total quantity of hours of human work and toil dedicated by the global workforce involved in the mammoth cooperative task of building the space station is around three-million people-years, or over 26 billion work hours. The obvious next question is how this compares with the other great cooperative feats of history, like the 400,000 people-years required to build the Great Pyramid of Giza, or the 100,000 people years to build the Coliseum in Rome, and whether these long run patterns signal an increase in humanity’s ability to cooperate at a vast scale.