the best education, shelter (a room only for the child), travel, cultural activities etc. In the past, when child mortality was high, people had more children, but invested less in them. Today, parents usually experience much less doubt about whether the child will live to adulthood, and so are more likely to strongly invest in that child. But strongly investing in each child makes it more difficult to have large numbers of children—a "quantity vs. quality trade-off" effect. Gender expectations and norms Social norms both within the family and in society at large determine fertility levels. The quality of couple relations in terms of support given to the woman matters, with studies on fertility in the high-income world showing a U-shaped relationship between gender equity within the couple and fertility: in countries with very low fertility rates, the probability of a woman to have the second child occurs at the extremes - either very low gender equality or very high gender equality. This is also reflected at a social level: countries that are neither sufficiently patriarchal to coerce women into having large families, nor sufficiently egalitarian to incentivize women to have more children through strong support (such as subsidized childcare and good support of working mothers), have very low fertility rates, especially among educated women. Where women are expected to 'choose' between their professional and public life, or having children, the more educated the woman is, the more likely she is to choose the former. The strong emphasis on the domestic role of women in Germany (unlike Scandinavia and France) was described as the cause of the very low fertility in that country. Historical effects The Greek historian Polybius largely blamed the decline of the Hellenistic world on low fertility rates, writing in his work The Histories that: In a speech to Roman nobles, the Emperor Augustus commented on the low birthrates of the Roman elite: Upon the establishment of the Roman Empire, Emperor Augustus would introduce legislation to increase the birthrates of the Roman nobility. Some believe that not only the Great Recession, but the Great Depression, may have been the result of a decline in birthrates overall. Clarence L. Barber, an economist at the University of Manitoba, pointed out how demand for housing in the US, for example, began to decline in 1926, due to a decline in 'household formation' (marriage), due, he believed, to the effects of