Finding the "B" value
(a.k.a y intercept)
Considering estimation, I believe my calculations are off. Mainly because "b" is almost always negative when according to the graph, it should be positive.
It is clear that in the beginning - 1950, the difference isn't immense. Later the difference is bigger until it reaches the past decade. From then on, the difference keeps getting smaller.
Here is a graph just to show you the population difference: