Positive relation between atheism and tax revenue as a percentage of the GDP

[buritobr]

The higher is the nonreligious population of a country, the higher is the tax revenue as a percentage of the GDP of a country.
http://en.wikipedia.org/wiki/List_of_countries_by_tax_revenue_as_percentage_of_GDP
http://en.wikipedia.org/wiki/Irreligion_by_country

Possible explanations
1. There is correlation but not causality. Countries which have high GDP per capita have also high tax revenue as a percentage of the GDP and high nonreligious population. We can observe that Sweden, Denmark, Netherland and France have very high nonreligious population and very high tax revenue as a percentage of the GDP. However, countries like the USA and Ireland are also very rich, but they have lower nonreligious population and lower tax revenue as a percentage of the GDP.
2. Religious people are more willing to support conservative policies
3. Religious organizations perform some roles of the state