The fertility opportunity hypothesis, by any name, was well received by ecologist Garrett Hardin, sociobiologists, numerous physical scientists, and mathematicians. "Fertility Decline No Mystery", reflects large increases in data supporting the fertility opportunity hypothesis. The economic collapse of former Asian tigers presented the opportunity for a prospective test of the economic opportunity hypothesis. The economic opportunity hypothesis suggests that a sense of contracting opportunity promotes low or declining fertility whereas the perception of expanding opportunity allows people to raise family-size targets. Mechanisms associated with small family size include delaying marriage or interrupting marital relations, abstinence before marriage, or protected sex. Social, cultural, and behavioral adjustments and intentional contraception can limit childbearing. As predicted by the economic opportunity hypothesis, fertility did increase during Peru's periodic export booms, and did decline during periods of recession. The economic opportunity hypothesis states that perceived shrinkage of opportunity discourages women or couples from embarking on marriage or reproduction.