Recent UN data from several nations on y = crude birth rate (number of births per 1000 population size), x1 = women’s economic activity (female labor force as percentage of male), and x2 = GNP (per capita, in thousands of dollars) has prediction equation ˆy = 34.53 −

0.13x1 − 0.64x2. The bivariate prediction equation with x1 is ˆy = 37.65 − 0.31x1. The correlations are ryx1

=

−0.58, ryx2

= −0.72, and rx1x2

= 0.58.

Explain why the coefficient of x1 in the bivariate equation is quite different from that in the multiple predictor equation.