Why do we use geometric mean for population density?

It is often used for set of numbers whose values are exponential in nature such as growth figures, population etc. It's use normalizes the range being averaged. In general, it is used when dealing with percentages to calculate growth rates. Human population growth is usually expressed as a percentage thus when the population growth needs to average, we use the geometric mean. For example: If the population of a town increases by 25% in a year, 30% in the 2nd year and 35% in the 3rd year. We can estimate the mean percentage growth in population. In this case we use the geometric mean. Hope this helps Also Geometric mean is also related to logarithmic distribution which equal to the exponential of the mean of log values. (Further workings available in booked sessions)