In Example 6 we used data from 1920 and projected to 2050 and found that the expected life span in the United States can be modeled as a function of the year of birth by

L(x) = 8.7744 + 14.907 ln x

where x is the number of years after 1900. Using data from 1920 to 1989, the model

ℓ(x) = 11.616 + 14.144 ln x

where x is the number of years after 1900, predicts expected life span as a function of birth year. Use both models to predict the life spans for people born in 2005 and 2021. Did adding data from 1990 to 2050 give predictions that were quite different from or very similar to predictions based on the model without that data?