Cafe Hayek: Is Niger's Problem Over-population?

In the comment section of this blog in an article on the famine in Niger, someone had commented that the basic problem in Niger was overpopulation, here is a response to that...
Cafe Hayek: Is Niger's Problem Over-population?: "Is Niger's Problem Over-population?

Inspired by the sad plight of the people of Niger, letters today in two major U.S. newspapers -- the New York Times and the Christian Science Monitor -- repeat the age-old myth that poverty is caused by over-population.

Let's look at just a few facts.

Niger's population density is 9 people per square kilometer. Compare this figure to the population densities of much more prosperous countries:

France: 110 people per sq. km.

Czech Republic: 133

Switzerland: 181

Italy: 197

Germany: 236

United Kingdom: 250

Japan: 340

Netherlands: 484

South Korea: 493

Taiwan: 636

Hong Kong: 6641

Now let's cheat big-time in favor of the overpopulation hypothesis by counting as relevant only Niger's arable land. If all Nigeriens lived only on Niger's arable land, the population density of this land would be 260 persons per square kilometer -- much denser than 9 persons per sq. km., but nowhere close to the population density (counting all the square kilometers, arable or not) of the likes of the Netherlands, South Korea, and Hong Kong.

(All facts reported above are calculated from data available at the CIA's World Factbook site.)

Where's the evidence for the apparently indestructible belief that over-population is a fundamental 'cause' of poverty?

The world needs more scholars of the likes of Julian Simon."