This comes from this data: https://www.rug.nl/ggdc/productivity/pwt/?lang=en
This specific chart comes from page 29 of this, which uses the above data: https://scholarworks.umass.edu/server/api/core/bitstreams/69ff54a4-6554-48b9-9b5b-58008cb25725/content
This comes from this data: https://www.rug.nl/ggdc/productivity/pwt/?lang=en
This specific chart comes from page 29 of this, which uses the above data: https://scholarworks.umass.edu/server/api/core/bitstreams/69ff54a4-6554-48b9-9b5b-58008cb25725/content