This "8 week" number thrown around by every company looking to teach people to code where did it come from? Does someone have an independent study that backs up

This "8 week" number thrown around by every company looking to teach people to code where did it come from? Does someone have an independent study that backs up the 8 week figure or is everyone choosing it because it sounds good? I love all these programs now and believe 8 weeks is enough to learn the basics. The goal after the program would be to instill a life long quest to better your skills each day not how much iOS makes you a hotshot.