I finished a post last week with the question of whether children are normal goods. Below I want to lay out some economic arguments on this, before putting in an evolutionary twist that raises the question of whether we can rely on any of the economic analysis. A normal good is a good for which demand increases with income. Cars, holidays and jewellery are examples of normal goods. The opposite is an inferior good, with demand decreasing as income rises.

Diane Coyle has noted the release of three new books on the evolution of cooperation: Wired for Culture by Mark Pagel, Beyond Human Nature by Jesse Prinz and Together by Richard Sennett. Each was reviewed by Robin McKie in the Guardian A quick glance at some reviews, such as this by Julian Baggini, suggests that evolution is at the heart of Pagel’s discussion of the development of culture, with a fundamental question being how does human culture affect transmission of genes.

As happens occasionally, I have just come across an article that I should have seen years ago. In an article titled Natural Selection on Male Wealth in Humans, Daniel Nettle and Thomas Pollet look at data from a variety of societies, ranging from subsistence groups to industrialised societies, and show that the link between male income and reproductive success is strong and ubiquitous. In their main analysis, they use longitudinal data for a group of British men born in a single week in March 1958.

After copping some criticism for his comments on the coverage of female contraception in health insurance, Steven Landsburg has noted that some arguments in its favour may have merit. Two of the more interesting he notes are as follows: We might not want to discourage parenthood in general, but surely we want to discourage parenthood by the sort of woman who won’t use contraception unless it’s subsidised. Ideally we’d tax childbirth among that class of women, but since they’re hard to identify, the best available policy is to subsidize contraception.

Even after controlling for observable traits such as IQ, married men earn more. Bryan Caplan suggests there are three economic explanations for this male marriage premium: Ability bias: Qualities that make a man attractive to a woman are also attractive to employers. Human capital: Marriage makes men more productive. Signalling: Marriage signals to employers that a man has desirable traits. Caplan notes a study that argues that ability bias accounts for less than 10 per cent of the premium.

From Daniel Kahneman’s Thinking, Fast and Slow: Much is therefore at stake in the debate between the Chicago school and the behavioral economists, who reject the extreme form of the rational-agent model. Freedom is not a contested value; all the participants in the debate are in favor of it. But life is more complex for behavioral economists than for true believers in human rationality. No behavioral economist favors a state that will force its citizens to eat a balanced diet and to watch only television programs that are good for the soul.

From When the Sleeper Wakes (1910): "What of the yellow peril?" he asked and Asano made him explain. The Chinese spectre had vanished. Chinaman and European were at peace. The twentieth century had discovered with reluctant certainty that the average Chinaman was as civilised, more moral, and far more intelligent than the average European serf, and had repeated on a gigantic scale the fraternisation of Scot and Englishman that happened in the seventeenth century.

To make his point that socioeconomic status is a major driver of educational outcomes, Dan Pink made the following chart. SAT scores are on the vertical axis, and family incomes on the horizontal axis. Sidestepping questions of what this correlation actually means, is there any plausible scenario that would result in a different relationship? If we assume, as many are using the chart to assert, that parental income “buys” higher SAT scores, then we will see SAT scores rising with income.

In Tim Harford’s discussion in Adapt of the benefits to experimentation , Harford notes that experimentation by individuals is often at great potential cost. As when a species evolves, what appears to be beneficial experimentation at a societal level involves frequent failure to survive by individuals. While Harford suggests that people should consider experimenting in a manner that avoids failure that threatens survival, the reality is that many people take risks with a large downside.

Natural selection operates through heritable variation in traits and differential reproductive success due to those traits. Many combinations of genes and mutations are failures, but the variation in traits creates a natural experiment in which highly evolved solutions to the environment can develop. In his excellent book Adapt: Why Success Always Starts with Failure, Tim Harford applies this evolutionary concept to business, war, accidents and other human pursuits. How did on-the-ground experimentation lead to a better outcome in Iraq?