Contribution years for full CPP benefits

Currently, the number of years of contribution for full CPP benefits is 39. However, it was not the case when CPP was first established. If you retire after one year of the implementation of CPP, you got full CPP benefit even if you only contribute for one year. Before 1986, the number of contribution years for full CPP benefits is 10. Between 1987 to 1996, the number of contribution years for full CPP benefits increased from 20 to 30. After 1997, it is 39. This is what I found from Copilot. There is little related information on internet. Please tell me if you know more.

Not only the number of years of contribution was low in the early years of CPP, but the contribution rate was also low. It was 3.6%. Today it is 11.9%. On top of that, there is CPP2, which requires further deduction.