Social capital is the component of human capital you build out of other people. It is the web of relationships — neighbors, classmates, professional societies, coworkers, mentors — that turns skill and knowledge into actual opportunity. Unlike the genetic and family endowment discussed at the end of this section, social capital is almost entirely developable: you choose where to stand, whom to stand near, and how to be useful. For a young adult deciding where to study or work, and for a parent deciding where to raise a child, this is one of the highest-leverage decisions on the board.
A strong network provides access to jobs, promotions, deals, and advice that never reach a public posting. Social capital is a multiplier on your human capital — the same skill earns far more inside a good network than outside one. Inherited social capital — the connections your family hands you — is simply a head start on that multiplier: a parent’s introduction, a relative’s mentorship, a family friend who vouches for you. If you were handed one, your job is to extend it and pass it on. If you were not, your job is to build it from scratch — and it can be built.
The research is consistent. Putnam’s Bowling Alone: The Collapse and Revival of American Community8 found that communities rich in social capital show better educational outcomes, lower crime, and faster economic growth. Granovetter’s The Strength of Weak Ties found that the highest-yielding job leads come not from close friends but from acquaintances — the people one step removed, who travel in circles you do not. Breadth of network, not depth, is what surfaces opportunity.
The most consequential finding is Chetty’s. Across two large studies,9,10 economic connectedness — the degree to which low- and high-income people are actually friends with each other — proved one of the strongest predictors of upward mobility ever measured. Other forms of social capital — civic participation, tight-knit communities, generalized trust — did not predict mobility. What moves a child up is not how neighborly the neighborhood is; it is whether the rich and the non-rich in it know each other.
Geography decides much of this for you. Low-income individuals make roughly four times as many of their friends inside their own ZIP code as high-income individuals do; the affluent form more of their friendships at college, because they are far more likely to attend. Place therefore constrains the poor far more tightly than the rich — the lower your starting point, the more your address is your destiny. You can inspect this directly: the Social Capital Atlas publishes exposure and friending-bias data for every high school, college, and ZIP code in the country. Treat it as a screening tool, not a curiosity.
The old boys’ network is real — so build your own The informal system by which the already-connected route jobs, deals, and capital to each other is not a paranoid fantasy. It is proximity, trust, and reciprocity operating among people who share institutions. You cannot abolish it, and resenting it changes nothing. You can join one — and build your children into one. The mechanics are unglamorous and entirely learnable:
You do not befriend your way into a wealthy peer group one person at a time — that is transactional, and transactional networking fails. You choose the room, and the room assigns your peers. Selective universities, certain employers, professional associations, nonprofit boards, alumni clubs, and a short list of neighborhoods come pre-stocked with the network. Pay the price of admission and the friendships form on their own.
A degree from a selective school is worth more as a membership card than as a transcript. Chetty found that universities are nearly the only venue where the wealthy reliably form friendships across class lines;10 high schools, workplaces, religious groups, and neighborhoods mostly do not. The credential buys a seat in the one room that mixes.
Stay loosely connected to many circles rather than deeply embedded in one. Keep in touch with former colleagues, classmates, and acquaintances — the contact you have not spoken to in two years is statistically the one who changes your career.
A network is a reciprocity system, and reciprocity starts with a deposit. Make introductions, share what you know, solve small problems for people before you need anything in return. A reputation for being useful and reliable compounds exactly like money.
For parents, this is the highest-leverage move in the chapter. Choosing a neighborhood and a school does not merely buy a child an education — it assigns the peer group, the parents standing behind that peer group, and the friending environment the child inherits for decades. Use the Social Capital Atlas the way you would use a school-ranking site.
Keep the proportion honest. A network is a multiplier, not an engine. Nearly every wealthy person first earned a high income; the network is what compounds that income into more. A superb network wrapped around a weak earner produces a well-connected person of modest means. The play is to build the earning power and stand in the right room — never to treat one as a substitute for the other.
Networks are not the only thing institutions sort. Marriage is too. Economists at the St. Louis Federal Reserve11 found that people increasingly marry partners with similar education and skills, and that this sorting accounts for roughly half the rise in household income inequality between 1980 and 2020 — education alone explaining about 35%. Two high earners marry, pool two incomes and two networks, and pull away from the household that pooled two modest ones. The university is not only where you meet your network; it is where you meet the person you compound it with.
There is a harder layer beneath this, and a book written for readers who intend to build something lasting should not flinch from it. Human capital is not assembled purely from schooling and effort. A substantial share of the traits that drive earnings — cognitive ability, conscientiousness, health, even height — is heritable. This is not fringe science: twin and adoption studies have measured it for decades, and genome-wide studies now build polygenic scores that predict a measurable slice of educational attainment — and of income itself — directly from DNA.12,13,14 Nearly every dimension of individual difference that bears on earning — risk tolerance, occupational choice, financial decision-making — carries some heritable component.15 People sort on these traits when they pair off, too — assortative mating is genetic as well as economic, and spouses are measurably correlated on the heritable correlates of education and height.16
Two cautions keep this honest. First, heritability is a population statistic, not an individual verdict: it describes how much of the variation in a trait tracks genes across many people — not a ceiling stamped on any one child. The malleable inputs — environment, schooling, social capital, the executive functions discussed next — remain large, and they are the entire subject of this book.17 Second, none of this licenses crude instrumentalism: you are choosing a life partner, not breeding stock. But pretending the genetic channel does not exist serves no one. Choosing a partner is, among other things, choosing your children’s endowment — the heritable floor, the household environment, and the network they inherit, all at once. Evaluate the decision with the seriousness you would give any other irreversible, multi-decade commitment. The economics of that commitment — prenuptial agreements, titling, the marriage penalty, and the cost of unwinding it — are taken up in chapter “The Economics of Marriage”.