第 1 章
The Economics of Desire: How Market Forces Shape Our Most Intimate Choices
When Casanova used lemons as contraceptives in the 18th century, he wasn't just being resourceful-he was participating in what economists now recognize as a fundamental cost-benefit analysis of sexual activity. This provocative insight comes from Marina Adshade's groundbreaking work that applies economic principles to our most intimate decisions. The book has become a favorite among both economics students and relationship experts, with figures like Dan Savage citing it as essential reading for understanding modern relationships. Beyond academic circles, it's sparked conversations about how market forces shape everything from college hookups to marriage patterns to infidelity rates. By viewing sex and love through an economic lens, Adshade doesn't reduce romance to cold calculation but rather illuminates how our seemingly personal choices reflect broader social and economic conditions. What makes this perspective so compelling is that it explains behaviors we observe every day but rarely understand in systematic terms.
第 2 章
The Sexual Revolution: An Economic Transformation
The liberalization of sexual values during the 20th century wasn't primarily a moral revolution-it was an economic one. New contraceptive technologies fundamentally altered the cost-benefit analysis of sex, transforming sexual behavior across society. The evidence is striking: in 1900, only 6% of unmarried 19-year-old women were sexually active, compared to 75% a century later.
Contrary to popular belief, birthrates began falling two centuries ago during the Industrial Revolution, not with the introduction of the pill in the 1960s. By the 1930s, average births had already dropped from seven children per woman in 1800 to just two. Throughout history, people used withdrawal, delayed marriage, and various other methods to prevent pregnancy. The first truly effective technologies included cervical caps (1838), rubber condoms (1850s), diaphragms (1882), IUDs (1909), and finally latex condoms (1912), which made protection both disposable and affordable.
The relationship between contraception and promiscuity is more complex than simple cause-and-effect. Research by Greenwood and Guner shows the pill itself contributed less than 1% to increased teenage sexual activity. Rather than one technology driving change, the pill was part of broader social shifts reducing stigma around premarital sex. The mathematical rise in out-of-wedlock births was inevitable: as contraception reduced births within marriage while premarital sex increased, the share of births to unmarried women naturally grew.
Different demographic groups face varying costs for sexual promiscuity. Women with little education or economic prospects face lower opportunity costs, while educated, economically independent women face higher potential costs but can better afford them. These costs include educational and career setbacks from mistimed pregnancies. As university enrollment has risen (from 24% to 41% between 1973-2009), with women now making up 60% of students, those without higher education face increasing marginalization in both economic and relationship markets.
Having children before marriage significantly limits options in the dating market. Dating profiles often explicitly reject potential partners with children, as they signal either promiscuity or reduced resources. As marriage rates decline (only 66% of unmarried 19-29 year-olds want to marry), the cost of promiscuity drops significantly. With lower marriage prospects, the economic penalty for premarital sex decreases by more than half.
While heterosexual promiscuity increases, gay men appear to be moving toward more committed relationships as societal acceptance grows. U.S. opposition to same-sex marriage dropped from 68% in 1996 to 44% by 2011. Economists Francis and Mialon found that in more tolerant states with no same-sex marriage bans, there are fewer anonymous meeting places for gay men and lower HIV rates. This differs from heterosexual patterns because increased tolerance allows gay men to form committed relationships without social penalties.
第 3 章
Campus Hookup Culture: Economics of the College Dating Scene
College students often believe they're having more sex than any previous generation, despite evidence showing university students have less sex than non-students of the same age. Today's university campuses have become favorable environments for men seeking casual sex, largely because women outnumber men. With more women than men on campus, men can easily find willing partners for casual sex, creating what economists would call a "buyer's market."
The campus sex market isn't driven by men wanting sex more than women, but by men's greater preference for multiple partners. The "price" being lowered isn't compensation for sex, but the level of commitment women can expect from sexual partners. Studies consistently show men desire more sexual partners than women-when asked how many partners they'd ideally like over two years, women typically answer one while men average eight. Similarly, 42 percent of men express interest in having multiple simultaneous partners compared to only 8 percent of women.
Binge drinking significantly contributes to campus promiscuity. Research from 136 U.S. colleges reveals that 46 percent of students reported binge drinking at least once in the previous month, with these students 25 percent more likely to be sexually active, 20 percent more likely to have unprotected sex, and 94 percent more likely to have multiple partners than non-binge drinkers.
When Halifax imposed minimum drink prices in 2007, research showed price increases do impact STD rates-Canadian economists found a 1% increase in beer prices lowers gonorrhea and chlamydia rates by 0.8%. However, college students may be less responsive to price increases since they consume like higher earners, anticipating future income. Some students may even drink specifically to enable sexual encounters.
When I ask students whether buying drinks for someone creates sexual obligation, female students protest while male students ask "how expensive were the drinks?" Research confirms this gender divide-when a man pays for an expensive date, male participants rated a woman's obligation for sex much higher (3.21 on a 6-point scale) than female participants did (1.85). This suggests that while female students may not explicitly feel obligated to have sex after a man pays, both genders recognize some correlation between spending and sexual expectations.
Counterintuitively, parents worried about their daughters' exposure to promiscuity might consider schools where men outnumber women, as this creates less female competition and more traditional dating patterns. Research confirms that students with multiple casual partners actually have sex less frequently than those in committed relationships, explaining why non-students in the same age group have more frequent sex than their college counterparts.
第 4 章
Digital Romance: How Technology Reshapes Relationship Markets
Online dating has created both opportunities and challenges for finding love. Unlike traditional dating, online platforms encourage users to filter potential matches based on quantifiable characteristics like age, height, and income, often eliminating promising partners who don't meet arbitrary criteria. This process turns "thick" markets into "thin" ones, potentially reducing match quality.
When shopping for pastries, we might eliminate categories but can reconsider if nothing else appeals. With online dating, potential matches are permanently filtered out before we ever see them. I've realized that people I've loved wouldn't have survived my online filters, nor would I likely have passed theirs. Online searches emphasize easily measurable qualities rather than experiential ones that truly determine relationship quality.
Online dating operates like a market with buyers and sellers trading off valued characteristics. Prices aren't monetary but represent opportunity costs when choosing partners. Extremely attractive people are "expensive" because everyone competes for their attention. When the market clears, expensive people pair with other expensive people, and so on down the line-a phenomenon economists call "assortative mating."
A study using data from Hot or Not revealed how competitive online dating is regarding physical attractiveness. Among 16,550 members, increasing someone's attractiveness rating by just one point increased their likelihood of receiving meeting requests by 130%. Men particularly pursued women more attractive than themselves, using a "shotgun approach" by being 240% more likely than women to click "Meet Me." Less attractive users initiated more contacts with much hotter users while ignoring equally attractive potential matches-suggesting most people overestimate their own market value.
People are remarkably biased in self-assessment-less than 1% of online daters rate their appearance as "below average," while 68% of men and 72% of women consider themselves "above average." This delusion affects behavior: less attractive people initiate more contacts with others significantly more attractive than themselves while ignoring equally attractive potential matches.
For women choosing between men, an unattractive man (bottom 10%) would need to earn approximately $186,000 more annually than a very attractive man (top 10%) to be preferred. For men, no amount of female income can compensate for lack of physical attractiveness-suggesting men either value appearance tremendously or care very little about income.
Korean economists found that even small signals, like sending virtual roses in an online dating experiment, had significant effects. When participants could send standardized messages to at most ten people, they were given two roses to signal sincere interest. Sending roses improved a participant's chance of having a date proposal accepted by 20 percent, working best when the sender was more desirable than the receiver.
Research shows online dating deceptions are typically minor-men add about an inch to their height while women subtract about eight pounds from their weight. However, less physically attractive people are significantly more likely to use misleading profile pictures and lie about objective measures like height and weight.
The increased efficiency of dating markets has contributed to income inequality as high-wage earners now more easily find and marry other high-wage earners. Online dating has reinforced economic class systems by facilitating assortative mating based on education and earning ability.
第 5 章
Marriage Economics: The Business of Commitment
Marriage serves two primary economic functions: efficient production of household goods and services, and insurance in bad times. While people may not always get their ideal partner, economic theory suggests we marry those of equal market value, though the most productive matches involve differences that exploit gains from trade.
Marriage produces three key benefits more efficiently than singlehood: regular sex with lower risks, biological children, and household goods and services. Research shows married people have more frequent sex than singles, with 76% reporting sex 2-3 times monthly versus 57% of never-married people. Marriage also provides the most cost-efficient way to have biological children with mutual commitment.
Most importantly, marriage allows couples to exploit comparative advantage in household tasks, with each partner specializing in what they do relatively better, even if one person might be absolutely better at both tasks. This explains why traditional gender roles emerged during industrialization-not from natural endowment but from men's comparative advantage in physical labor, which changed as the economy evolved to value mental over physical abilities.
Research by Victoria Vernon reveals the economic value of marriage varies by income level. Married women in high-income households gain about 34 minutes of free time daily compared to single counterparts. However, married women in low-income households actually work 15-48 minutes more daily, depending on whether they have children. Despite gaining free time, high-income married women still do more housework than single women-spending 31-41 minutes more cleaning, 41-50 minutes more cooking, and 8-11 minutes more running errands daily.
Singles flock to cities for two compelling economic reasons: lower search costs and higher quality matches. In densely populated areas, people encounter more potential partners daily, making the search for love more efficient. When search costs are lower, people set higher reservation values for potential partners, refusing to settle and holding out for better matches.
This explains why educated singles, particularly women, struggle in urban marriage markets. With more women than men completing college, and educated women traditionally preferring better-educated men, there's a numerical imbalance. Research shows cities with high male wages attract disproportionately more women than men, as women strategically position themselves in marriage markets.
Economist Gustaf Bruze's study of Hollywood's top 400 actors reveals surprising marriage patterns. Despite fame and fortune disconnecting their income from education, stars still tend to marry partners with similar education levels-much like the general population. This suggests educational matching provides benefits beyond income indicators, likely creating intellectual and experiential commonality.
Research by Charles, Hurst, and Killewald reveals that parental wealth significantly influences marriage patterns. Men with parents worth less than $1,000 are more than twice as likely to marry women from similarly low-wealth backgrounds than random matching would predict. Similarly, men with parents worth over $100,000 are 60% likely to marry women from wealthy families, far exceeding the 39% random chance. This sorting reinforces economic inequality across generations.
第 6 章
Marriage Institutions: How Society Shapes Commitment
Marriage functions as an economic institution-a set of rules and beliefs governing social behavior. Unlike sociologists who debate marriage's definition, economists see it simply as actions that define family within a community. This institutional view recognizes marriage varies across communities and evolves over time. While individuals can't choose their community's marriage institution, economic factors determine how these institutions develop.
Marriage organization has evolved with food acquisition methods. Early foragers had no long-term mating, just sex with multiple partners in exchange for food sharing. As humans moved to savannas, increased meat consumption meant babies required more maternal care, leading to serial monogamy lasting about four years-long enough to ensure offspring survival. With agriculture's rise, especially after the plow's invention, gender-divided tasks emerged and men could accumulate wealth.
Using Bill Gates's 66,000-square-foot mansion as a hypothetical scenario, I explore why wealthy nations institutionalize monogamy rather than polygyny. If Gates wanted a second wife, who would be harmed? While Melinda might be psychologically worse off, her economic well-being wouldn't diminish in such a vast home. Yet industrialized nations prohibit such arrangements for two key reasons: First, educated women like Melinda have significant marriage market power and can find monogamous partners without sacrificing much wealth. Second, polygyny creates a mathematical reality where some men become completely excluded from marriage.
Using a concept called Pareto efficiency, I illustrate why certain marriage arrangements persist through a simple stick-figure model. With three men of varying wealth and three identical women, polygyny naturally emerges when women can freely choose-the wealthiest man attracts multiple wives while the poorest remains unmarried. Both monogamy and polygyny can be Pareto efficient depending on starting conditions. Imposing monogamy helps poorer men but restricts women's choices.
When polygyny leaves many men unmarried, demand for prostitutes increases, driving up prices for sex. This economic pressure can make prostitution more attractive to some women than marriage, explaining why polyandry (multiple husbands) rarely coexists with polygyny.
Why does monogamy persist in Western nations despite widening income inequality? The answer lies in industrialization's effects on child-rearing economics. In industrial societies, education became more valuable than brawn, shifting preferences from many uneducated children to fewer, better-educated ones. Wealthy men in industrial nations have high incomes due to human capital rather than land resources, and they seek educated wives who can help produce "high-quality" children. This increases the value of educated women in the marriage market, giving them more bargaining power.
The acceptance of same-sex marriage represents a significant institutional evolution in recent decades. Gallup polls show a 23-percentage-point decline in opposition to same-sex marriage over just fifteen years in the United States. While younger generations are more accepting (the "cohort effect"), this accounts for only 33% of the attitude shift between 1988-2006. Most change comes from individuals changing their personal beliefs.
第 7 章
Power Dynamics: The Economics of Household Decisions
Economic forces have dramatically transformed marriage dynamics by reshaping bargaining power between spouses. Jane's marriage story illustrates how economic power shapes relationship dynamics. At 19, she married John, nine years her senior, trading her youth for his financial stability. Moving across the world, Jane found herself in a relationship where her lack of income and younger age left her with no bargaining power. John unilaterally made decisions about where they lived, whether to have children, their social circle, household chores, and intimacy.
Research shows women who take their husband's name face significant professional disadvantages. Employers perceive them as less intelligent, less ambitious, and more family-focused than name-keepers. Experimental studies reveal women who change their names receive fewer job offers and lower wages. Education strongly correlates with name choices-women with master's degrees are 2.8 times more likely to keep their names than less-educated women, while those with doctorates are 9.8 times more likely.
Economists view marriage as a negotiation system where "bargaining power" determines each partner's influence over decisions-from resource allocation to childcare to sexual relations. Equal bargaining power means each partner has a 50% chance of prevailing in disagreements, while imbalanced power leads to one-sided decisions. Historically, men's comparative advantage in market work gave them greater bargaining power. Over the last half-century, however, three factors have shifted this balance: women's increasing relative wages, technological advances in home production that reduced domestic labor needs, and growth of affordable service sectors that replaced traditional household work.
India's online dating market reveals how economic uncertainty reshapes marriage preferences. Following the global recession, Indian women seeking husbands shifted their focus from high-earning non-resident Indians in technology and finance toward local civil servants with more predictable incomes. Simultaneously, Indian men increasingly sought employed women-searches for working brides rose 15% in 2008 alone.
The educational landscape of marriage has transformed dramatically. In 1970, 28% of husbands had more education than wives, yet only 4% of women outearned their husbands. By 2007, just 19% of husbands were more educated than wives, while 22% of women earned more. Despite assumptions that educated women might divorce more readily, research shows the opposite: those without high school diplomas have a 16% divorce chance, high school graduates 10%, and postgraduates below 3%.
Income inequality drives divorce rates higher. While the bottom 20% of earners saw only a 9% income increase between 1979-2003, the top 1% enjoyed a staggering 201% increase. This creates a "keeping up with the Joneses" effect where everyone increases consumption to match the visible spending of wealthier neighbors. Research shows a 1% increase in county-level inequality correlates with a 1.2% rise in divorces.
Female-to-male transsexuals provide unique insights into workplace gender discrimination. Sociologist Kristen Schilt found that post-transition, white transmen experienced greater authority, respect, and support than they had as women. The same opinions that were previously sanctioned were now rewarded, and they received better resources, improving job performance and income.
Research by Negrusa and Oreffice reveals that lesbian couples save significantly more than both gay male couples and heterosexual married couples. Using mortgage payment-to-home value ratios as a savings measure, lesbian couples pay nearly 9% more on annual mortgages than other couples, even after controlling for factors like age, education, and children.
第 8 章
Teen Sexuality: Economic Incentives and Social Outcomes
Economic factors profoundly shape societal views on adolescent sexuality. Historically, shorter lifespans led to lower ages of consent, while limited agricultural land created pressure to delay marriage to control population growth. Today, the economic return on education influences disapproval of teen parenthood, while housing wealth affects children's exposure to sexual knowledge.
Research on Canada's 2009 age-of-consent increase (from 14 to 16) revealed that younger teens make equally sound sexual decisions as older teens. Among 26,000 adolescents studied, 14-15 year-olds were no worse at sexual decision-making than 16-17 year-olds. Teens in the affected age group overwhelmingly had partners their own age, with less than 5% having first experiences with adults five years older. Younger teens were equally likely to avoid sex under substance influence and significantly more likely to use condoms (83% vs 74%) than older teens.
American teenagers today are less sexually active than any generation since the mid-1980s, with less than half having had sexual intercourse compared to 51% of women and 60% of men just 22 years earlier. They're not substituting other sexual behaviors either-nearly half of teens 15-17 report no sexual contact whatsoever. Despite high contraceptive use (92% of sexually active male teens and 86% of females), the US maintains the developed world's highest teen birth rate.
When schools draw students from vastly different socioeconomic backgrounds, teen pregnancy rates often soar. Economists Kearney and Levine argue that high income inequality creates a "culture of despair" among disadvantaged teens who perceive little cost to early pregnancy, believing they can't escape their circumstances regardless. Their research shows teenage women from low socioeconomic backgrounds in high-inequality states are 5 percentage points more likely to give birth by age 20 than similar women in low-inequality states.
When college seems financially unattainable, teens have less incentive to avoid pregnancy. Economist Benjamin Cowan found that a $1,000 reduction in community college tuition decreases the average 17-year-old's sexual partners by a remarkable 26%. Lower college costs also reduce smoking (14%) and marijuana use (23%). This suggests teens rationally consider how current risky behaviors might impact future opportunities.
Paradoxically, as teen promiscuity has reached a twenty-year low, STD rates remain alarmingly high, with 50% of new infections occurring in people under 24. Gender imbalances in schools create power dynamics where men hold greater bargaining power-when grade-twelve boys outnumber girls, girls report having more sex than they want while boys have as much as they prefer. This power imbalance extends to condom use decisions, with men (who face lower infection risks) often deciding against protection.
第 9 章
Infidelity Economics: The Market for Extramarital Affairs
The chapter opens with Google's "predictive queries" for marriage terms revealing common marital problems. Infidelity's prevalence is difficult to measure precisely, with rough estimates suggesting 50% of people cheat during marriage. More reliable studies indicate about 7% of women and 14% of men in first marriages admit to extramarital sex, though these figures underestimate actual rates since divorced individuals (who have higher rates of reported infidelity) are excluded from such studies.
Economist Fabio D'Orlando notes that increased social acceptance of swinging has led to more participation and more radical sexual activities among married couples. As internet access has reduced the risks and costs of finding like-minded couples, swingers have moved from "softer" to "harder" sex acts, increasing demand for single men at these events.
Dynamic inconsistency theory applies to marital infidelity. When preferences change over time, initial threats (like leaving an unfaithful spouse) may not remain credible when infidelity actually occurs. For example, a husband who threatens to leave if his wife cheats may find himself unwilling to follow through after discovering her infidelity. Solutions include formal commitments like prenuptial agreements.
Infidelity can be understood through economic cost-benefit analysis. The expected cost equals the probability of being caught multiplied by the probability your spouse will leave multiplied by the cost of divorce. For example, a financially dependent homemaker with a 30% chance of being caught, 50% chance her husband leaves, and $100,000 loss faces an expected cost of $15,000. Meanwhile, a working woman with only 5% chance of discovery, same 50% chance of husband leaving, and $50,000 loss faces just $1,250 in expected costs.
Humans, like other mammals, aren't naturally monogamous. The "Coolidge Effect" explains how males lose interest in repeated copulation with the same partner but regain interest when a new partner appears. Evolutionary theory suggests men are hardwired for multiple partners because historically, more partners meant more offspring. Women, limited in reproduction quantity, evolved to seek quality partners instead.
Oral contraceptives eliminate the biological preference for masculine-appearing men that naturally occurs during ovulation. When women stop taking birth control to become pregnant, their suppressed biological imperative for masculine mates suddenly returns, potentially making their chosen partner seem less desirable.
Research by Elmslie and Tebaldi supports the link between infidelity and fertility patterns. Men's likelihood of cheating increases with age until 55, then declines. Women's infidelity peaks earlier-around age 45-coinciding with declining fertility. Contrary to expectations, more educated men are actually less likely to cheat than those with only high school education.
Despite media coverage suggesting wealthy men cheat more frequently, research shows no significant correlation between a man's income and his likelihood of infidelity. The real income effect applies to women-those in poorer households are significantly more likely to be unfaithful than those in wealthier ones.
Research consistently shows that people who cheat in marriages report being less happy. Married women who are "not too happy" are 10 percentage points more likely to cheat than "very happy" women, while unhappy men are 12 percentage points more likely to be unfaithful. A seventeen-year study by Previti and Amato reveals that infidelity is typically the consequence of an already unhappy marriage rather than its initial cause. However, infidelity further deteriorates marital quality, increasing the likelihood of divorce.
第 10 章
Romance in Later Life: New Market Dynamics for Seniors
The infamous 1986 Newsweek cover story predicting dismal marriage prospects for single women over 30 proved wildly inaccurate. By 2010, 75% of college-educated women who were 30 and single in 1986 had married, along with 69% of those who were 35, and 68% of those who were 40. Despite alarming headlines, most people still marry during their lifetimes.
Research by Hankins and Hoekstra reveals that financial windfalls affect women's and men's relationship decisions differently. Single women who won larger lottery amounts ($50,000) were 40% less likely to marry within three years than those who won smaller amounts ($1,000). This suggests financial independence gives women the freedom to be more selective about marriage or avoid sharing control of their money.
The market for late-in-life romance has become increasingly "thick" with more participants and better-quality relationships. Several economic factors explain this trend: First, people are postponing first marriages due to desires for smaller families, access to fertility treatments, and changing appearance expectations. Second, contraception and changing social norms allow singles to be sexually active without marriage, giving them more time to search for ideal partners. Third, improved home production technology and purchasable services have made both genders more self-sufficient.
Research shows height significantly impacts men's marriage prospects. Studies find taller men earn higher incomes (about 4% more for men 2-4 inches above average height), but even controlling for income, women prefer taller men. Online dating research reveals a short man would need to earn over half a million dollars annually for a woman 5 inches taller to consider him.
Despite the common assumption that older men dominate the senior dating market, the reality is more complex. While women outnumber men three-to-one among those over 65, older women are increasingly selective, not desperate. They're often more willing to remain single than accept an inferior arrangement, particularly one that might involve caregiving responsibilities.
STD rates are alarmingly rising among adults over 50, with HIV/AIDS cases increasing fastest among those 60-64. Despite this, only 25% of sexually active men over 50 with multiple or new partners report using condoms. The risk calculation is complex: while older adults have lower STD rates than younger people, older men are more likely than older women to carry infections. Women face higher transmission rates when exposed-a woman's risk of contracting HIV from an infected male partner is three times higher than vice versa.
When I was 36, a dinner party turned awkward when my hosts tried to set me up with a 53-year-old man. Research shows the older spouse typically has more bargaining power in heterosexual marriages-a wife five years younger than her husband works about ten more hours annually while he works eleven fewer. About 17% of newly married women ages 40-65 married men more than five years younger-a dramatic increase from just 3% in the 1970s. This "toy-boy" trend correlates with women's increased education and economic success.
