That .80 constitutes a stronger relationship with livability than with any other variable considered. Keep in mind, the importance of IQ underestimated by this method, as many of those variables are part of the 44 used to gauge livability--in this sense, they have a built in statistical advantage that the IQ estimates do not have. Other correlations with livability include:
Illegitimacy rate (-.68)
Average life expectancy (.62)
Racial composition of the population (.62)
% of the population with a bachelor's degree or greater (.56)
Violent crime rate (-.54)
Unemployment rate (.50)
Per-student educational expenditures (.45)
Gun ownership rate (-.44)
Median age (.20)
It even 'explains' slightly more than the poverty rate (r-values of .801 to .797) does, the only variable that approaches IQ's significance. Interestingly, though, IQ and poverty correlate at a more modest than expected .59. They do not relate to livability in the same way, but instead act as the two primary pillars on which it rests.
Murray and Herrnstein showed that greater intelligence decreases the probability of becoming impoverished (from The Bell Curve, p135):
Imagine a white person born in 1961 who came from an unusually deprived socioeconomic background: parents who worked at the most menial of jobs, often unemployed, neither of whom had a high school education (a description of what it means to have a SES index score in the 2d centile on socioeconomic class). If that person has an IQ of 100-nothing special, just the national average-the chance of falling below a poverty-level income in 1989 was 11 percent. ...Going in the other direction, a reduction in poverty, especially as it relates to ensuring that basic nutritional needs are met, bolsters IQ somewhat.
Conversely, suppose that the person comes from the 2d centile in IQ but his parents were average in SES status-which means that his parents worked at skilled jobs, had at least finished high school, and had an average income. Despite coming from that solid background, his odds of being in poverty are 26 percent, more than twice as great as the odds facing the person from a deprived home but with average intelligence.
We've been waging the War on Poverty to reduce it for half a century now, yet we're in the same spot we were in at the end of the sixties. Erstwhile, the corresponding War on Unintelligence, or more palatably, the Crusade for Intelligence, has not yet been forthcoming (or has been comparable to the first wave led by Peter the Hermit in the form of No Child Left Behind). It's long past time we attack a low quality of life on two essential fronts.
The Bell Curve brought to the public mind the importance of IQ in the US, and data marshalled in IQ and the Wealth of Nations evinces how meaningful it is at the national level. It's not everything, but it's increasingly becoming clear that it is quite a lot. Raising it should become a primary policy goal.
Inevitably, such an approach will be criticized for insinuating the moral worth of people based on an attribute that is largely beyond their control. That kind of posturing is, however well-meaning, injurious.
Why not make the same argument about attempts to reduce obesity or the prevalence of autism? If there are ways to increase physical fitness or reduce the number of children born with autism, through a systematic revamping of foods to have a lower glycemic index or by encouraging men to have all their children before they reach their fifties, does that too insinuate that obese or autistic people are of lesser moral worth? Is such didactic posturing worth increasing the prevalence of obesity or autism?
In the forceful words of Randall Parker:
Anything that could raise average IQ a few points would do more to boost economic growth and lower social pathologies than increased educational spending or the other typical liberal or free market libertarian nostrums.To oppose methods to boost average IQ (incentives for the wealthy/intelligent to have more children, the poor/unintelligent to have fewer, ensuring adequate iodine intake and vitamin consumption for impoverished children, a merit immigration system, discouraging the use of mind-altering substances), or even the discussion of potential ways to do so, must be challenged with this: There is nothing socially or economically benign that correlates inversely with IQ. I believe that is about tautologically true--I've come across nothing to the contrary, except for fecundity, which is debatably desirable.
++Addition++ Randall Parker and Arnold Kling weigh in.