A discount rate should be constant across equal time intervals; if it appears to vary (preferring money-now in the near comparison but waiting in the far-shifted comparison), that inconsistency reveals present-bias rather than a stable preference.

There is no fourth type of person — someone who would want to save now but spend in the future — they essentially do not exist in the data.

Natalie Portman claimed that with microfinance, eradicating poverty takes just 'a mouse click' — a claim Munger flags as illustrative of the overhyped optimism around microfinance.

Mobile-phone-based payments may leapfrog much of the microfinance apparatus, enabling savings and payment transfers via cell phones within roughly ten years.

Banks add value by aggregating dispersed savings (safer than burying money) and lending it out, profiting from the spread between deposit and loan rates, which is why accumulating money in one secure place is more efficient than mattresses and backyards.

Many developing nations are effectively 'disintermediated' — they lack the financial intermediaries (safe savings accounts, payment transfers, credit, insurance) that rich countries take for granted, so people must transact in cash and rely on local moneylenders charging 200% interest.

The widely held conventional wisdom — that poor people are credit-constrained, and giving them access to capital lets them invest in small equipment and escape poverty (echoing Hernando de Soto's collateral argument) — turned out to be false: controlled studies show no measurable effect on poverty.

Boudreaux and Cowen argued (in their 2008 Wilson Quarterly article) against the prevailing enthusiasm by claiming microfinance's effects are small and that its most important function is not lending but enabling saving — a view that became conventional wisdom roughly three years later.

For some poor people the implicit rate of return on saving is sharply negative — Cowen estimates around minus 75% in central Mexico and an Indian study finds around minus 30% — because holding cash triggers obligations: relatives borrow and don't repay, village festivals demand contributions, or a husband spends it, so one must save nearly four times the target to net it.

Microfinance reduces the price of saving: even though microfinance savings groups yield a negative ~30% return, that is better than the minus-75-to-80% an individual faces alone, so the intervention makes saving cheaper rather than profitable.

If poverty were truly just credit constraint, the problem would self-correct: people facing 20-30% returns on investment would save, invest, and profit, and lenders would profit serving them — so the persistence of poverty is itself proof the binding constraint is not credit.

A subset of borrowers who take genuine commercial-style loans (e.g., $200 repaid over a year to fund a soldering iron and assemble motherboards) can earn 15-20% returns; these are commercially viable and increasingly served by ordinary commercial banks, so this is not the segment microfinance uniquely addresses.

The Grameen Bank model has a borrower in a circle of 7-8 receive ~$40, immediately repay $4, then pay $4 weekly for 9-10 weeks, ending at $44 total — roughly 20-24% interest — which is expensive but far cheaper than a moneylender, and the group structure provides culturally appropriate enforcement.

Microfinance functions as 'saving down': the borrower receives $40 up front, spends it on consumption (food, education, medicine), then pays it off over time — reversing the normal 'save up then spend' pattern — and the group obligation and threat of shame/shunning provide the commitment device that makes repayment possible where saving alone is not.

The same social-obligation forces that make saving costly also make it hard for women specifically to borrow or hold money, which is why Grameen targeted women — and why the savings constraint and the gender constraint share a common cause.

Jonathan Morduch's survey design — asking people to choose between a smaller sum tomorrow vs a larger sum three months later, and the same comparison shifted a year into the future — reveals three behavioral types, and the microfinance-successful borrowers are disproportionately the 'type 3' who take money now but reveal a low discount rate when the choice is shifted to the future (they want to save but can't).

Institutions are not necessarily efficient; following Douglass North, institutions can be highly inefficient or even pathological because institutional evolution lacks the selection pressures (mergers, natural selection) that weed out bad forms — so dysfunctional poverty-perpetuating norms can persist for a very long time.

The community-insurance obligation is simultaneously a benefit and a curse: in the absence of formal insurance, mutual obligation insures everyone against bad shocks, but it is precisely that obligation to share that makes individual saving impossible.

The phenomenon resembles professional athletes who sign large contracts yet go bankrupt: coming from poor strata where obligation norms prevail, they feel compelled to buy houses and cars for family and friends, effectively a private rent-seeking tax on sudden wealth.

Buying an indivisible asset like a cow is a savings strategy precisely because neighbors cannot ask for 10% of a cow, whereas cash savings invite the question 'do you have any money?' — so converting savings into lumpy, non-divisible, hard-to-observe forms protects them from social claims.

A randomized study ('Are Women More Credit Constrained?') found no measurable difference in rate of return between those given grants and controls, but there was almost certainly a significant quality-of-life difference from modest spending on education, medicine, and small assets — so aggregate poverty measures are not the best test of microfinance's value.

The ideal savings 'bank' in this environment would deliberately be open only briefly and impose high withdrawal costs (draconian anti-consumer rules), because the friction itself is the value — it lets a saver honestly say 'the bank is closed, I can't get my money' to deflect a relative's claim.

Institutional evolution lacks the selection mechanisms of markets and biology: there is mutation (variety of forms) but no mergers/acquisitions or natural selection pruning inferior institutions, so better institutions displace worse ones only in the very long run — Munger prefers Hume's view of accepted conventions over Hayek's efficiency-tending evolution.

The deeper barrier to escaping poverty is the lack of physical capital: with little capital, the marginal product (and wage) of labor — especially educated women's labor — is low, so educating women has low economic payoff; only capital accumulation raises labor's marginal product enough to make women's education economically inevitable (an Adam Smith point).

The Gates Foundation redirected $100 million previously pledged to microfinance toward subsidizing the creation of secure local savings banks, but so far that effort has had no measurable aggregate impact.

Even offering a zero rate of return induces saving, because the alternative (holding cash) carries a negative return.

There is a circular trap: loans are unprofitable because there is too little saving, and saving is investment, so there is too little capital to raise wages to the point where investment becomes profitable — breaking this circle is the core development problem.

Microfinance circles provide two kinds of insurance: intertemporal smoothing (a missed payment can be made up later) and cross-sectional risk-pooling (the whole group is jointly responsible for the loan, with explicit reciprocity over time).

Microfinance is not a single thing but a bewildering array of at least 20 different mechanisms — some for loans, some to facilitate saving, some to speed payment transfers.