Common Sense: The Investor's Guide to Equality, Opportunity, and Growth
Summary
Greenblatt, who runs Gotham Capital and wrote The Little Book That Beats the Market, applied his analytical habits to public policy questions in this short book.
His method is to ask what actually produces the outcome in each case and to look for the intervention with the best return per dollar. On education he argues from the charter school lottery evidence, which uses random assignment among applicants to identify the effect of attending, that certain school models produce large measurable gains for low-income students, and that expanding what works rather than reforming what does not is the higher-return approach. He was personally involved in funding schools in New York, which informs the discussion.
On banking he proposes narrow banking arrangements that would separate deposit-taking from risk-taking, on the argument that government guarantees of deposits inevitably subsidise the risk-taking attached to them.
On monetary policy he argues that quantitative easing operated primarily by raising asset prices and therefore benefited existing asset holders, and he proposes alternative mechanisms for putting money into the hands of people who would spend it.
On immigration, on job training and on other questions he applies the same approach: identify the measurable effect and the cost.
The book is short and written for general readers. Its strength is the insistence on evidence about what works rather than on ideological position, and Greenblatt is explicit that he is applying an investor's habits to fields where he is not an expert. The charter school evidence he relies on is genuine but contested in its generalisability, since lottery studies identify the effect of the schools that are oversubscribed rather than of the sector. His policy proposals are sketches rather than developed programmes.
Key takeaways 7
- Charter school lottery studies use random assignment among applicants, which identifies the effect of attending rather than of who applies.
- Expanding school models that measurably work produces better returns than reforming those that do not.
- Government guarantees of bank deposits inevitably subsidise the risk-taking attached to the same institutions.
- Separating deposit-taking from risk-taking would remove the subsidy without eliminating either function.
- Quantitative easing operated by raising asset prices, which benefited people who already held assets.
- Policy questions should be assessed by measurable effect per dollar spent rather than by ideological position.
- Lottery studies identify the effect of oversubscribed schools, which limits what they establish about the sector as a whole.
Who should read it
Readers who want an investor's evidence-first approach applied to education, banking and monetary policy, treating the proposals as sketches.
About Joel Greenblatt
Founder of Gotham Capital (1985) and Managing Principal of Gotham Asset Management; long-time adjunct professor at Columbia Business School
You Can Be a Stock Market Genius is the standard text on special-situations investing, and the Magic Formula books turned quantitative value into a method ordinary investors can follow.
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