Life insurance rates are based on life expectancy values compiled for large demographic groups. But with improvements in medical care and nutrition, life expectancies have been changing. Here is a table from the National Vital Statistics Report that gives the Life Expectancy for white males in the United States every decade during the last century (1 = 1900 to 1910, 2 = 1911 to 1920, etc.). Consider a linear model to predict future increases in life expectancy. Would re-expressing either variable make a better model?

Decade 234 5 6 7 8 910 Life exp. 486 544 597 62.1 665 674 68.0 70.7 727749