A new study has found that nations with bigger governments tend to have happier populations, but only in high IQ countries. Obydenkova and Salahodjaev (2017) looked at the relationship between government size, defined as government spending as a percentage of GDP, IQ, and national subjective well-being (SJW), as measured by a questionnaire administered to 3,000+ people per nation, across 147 countries.
They found that both IQ and government size positively correlated with national happiness, as did economic development (GDP per capita). Ethnic diversity, income inequality (GINI), and being in Africa were all found to predict lower than average subjective well-being.

Some might suppose that countries with larger governments only tend to be happier because they are wealthier, or because their populations are smarter, or because they tend to have less income inequality.
Such hypotheses are conceptually reasonable, but they were all refuted by the finding that government size continued to predict higher national happiness even after controlling for IQ, GDP per capita, income inequality, ethnic diversity, and whether the country was in Africa.
This on its own is an important finding which libertarians will need to grapple with: populations with bigger governments tend to be happier than populations with small governments, even when the populations being compared are equally wealthy.

There was also a significant interaction between government size and IQ meaning that government size was more strongly linked to national well-being among high IQ nations. Obydenkova and Salahodjaev broke this interaction down by looking at the correlation between government size and subjective well-being just in countries with above and below average IQ.
Among high IQ nations, a significant correlation of 0.38 was found between government size and national happiness:

This was not the case among low IQ nations. In these countries, IQ had a statistically insignificant correlation of -.01 with national happiness:

Obydenkova and Salahodjaev hypothesize that high IQ populations may be better at electing non-corrupt governments that do what they want. If this is true, it would make sense that a bigger government would not lead to happier people in low IQ nations where governments tend to be more corrupt and to act independently of the will of the populous.
Another possibility, fully consistent with the one just offered, is that low IQ populations are more vulnerable than average to the negative effects of a welfare state. To the degree that variation in government spending among low IQ nations reflects variation in welfare spending, this study supports that narrative as well.
Another interesting finding of this study is that economic inequality is positively correlated with national happiness after controlling for government size, wealth, IQ, etc. This finding poses a difficulty for those, normally liberals, who argue that economic inequality damages national well-being independently of these other variables.
Returning to IQ, it would be interesting to see what these results would look like if social cohesion was controlled for. Higher IQ people tend to be more trusting and pro-social, and tightknit communities may tend to feel better than atomized ones about government projects and welfare spending.
I’d also like to see this broken down by policy. My hunch is that some kinds of government spending, such as spending on needed public infrastructure, benefit both high and low IQ populations while other kinds of spending, such as on welfare, benefit high IQ populations far more than they do low IQ ones.
Regardless, this paper provides yet another demonstration of the importance of considering a population’s IQ when analyzing government policy.