Can one generalize the defining concepts of a circle and ellipse to shapes defined by three or more foci?

Can this become a fruitful classroom investigation?

Can this become a fruitful classroom investigation?

How Closely do Geographic Factors Determine Population?

I tried to see if a country's population is proportional to its area times average rainfall (i.e. total amount of precipitation). With my best approximation, a linear function $\text{Population} = k\times \text{Area}\times \text{Rainfall}$, I was still off by an average of $80\%$ for each country.