One of the core principles of the Acton Institute mitment to wealth creation since material impoverishment undermines the conditions that allow humans to flourish. We consider helping our fellow citizens to escape material deprivation to be one of the most morally significant economic concerns of our age. But how to do we gauge whether our neighbors are able to improve their economic security? A key metric that is often used is e or social mobility, the ability of an individual to improve their economic status over time.

Last month I noted a study that highlighted four broad factors that appear to affect e mobility:

1. The size and dispersion of the local middle class,

2. Two-parent households,

3. Better elementary schools and high schools, and

4. Civic engagement, including membership in religious munity groups.

Saying that schools should be “better” is unhelpfully vague. But a recent article in City Journal by E. D. Hirsch, Jr., explains just what qualitative factor is most important: The key to increasing upward mobility is expanding vocabulary.

Hirsch’s article is one of the most important essays on education published this year — perhaps even of the decade. I highly encourage you to read the entire feature. But if you only have time for a bullet-point presentation, here are ten key facts and mendations from Hirsch’s brilliant article:

1. [T]here’s a positive correlation between a student’s vocabulary size in grade 12, the likelihood that she will graduate from college, and her future level of e. The reason is clear: vocabulary size is a convenient proxy for a whole range of educational attainments and abilities—not just skill in reading, writing, listening, and speaking but also general knowledge of science, history, and the arts. If we want to reduce economic inequality in America, a good place to start is the language-arts classroom

2. The decline in the educational productivity of our schools tracks our decline in e equality. For 30 years after 1945, Stiglitz observes, economic equality advanced in the United States; after about 1975, it declined.

3. The dilution of knowledge and vocabulary, rather than poverty, explains most of the drops in test scores from previous decades.

4. Vocabulary doesn’t just help children do well on verbal exams. Studies have solidly established the correlation between vocabulary and real-world ability.

5. The military entrance exam, the Armed Forces Qualification Test (AFQT), consists of two verbal sections (on vocabulary size and prehension) and two math sections. The military has determined that the test predicts real-world job performance most accurately when you double the verbal score and add it to the math score. Once you perform that adjustment, according to a 1999 study by Christopher Winship and Sanders Korenman, a gain of one standard deviation on the AFQT raises one’s annual e by nearly $10,000 (in 2012 dollars).

6. There’s no better index to accumulated knowledge and petence than the size of a person’s vocabulary. Simply put: knowing more words makes you smarter.

7. If vocabulary is related to achieved intelligence and to economic success, our schools need to figure out how to encourage vocabulary growth.

8. The fastest way to gain a large vocabulary through schooling is to follow a systematic curriculum that presents new words in familiar contexts, thereby enabling the student to make correct meaning-guesses unconsciously.

9. Because vocabulary is a plant of slow growth, no quick fix to American education is possible. That fact accounts for many of the disappointments of current education-reform movements.

10. It isn’t overstating the case to say that the most secure way to predict whether an educational policy is likely to help restore the middle class is to focus on the question: Is this policy likely to expand the vocabularies of 12th-graders?

Hirsch’s final question is key. When we consider educational reforms, the primary question we should be asking is how it will expand the vocabularies of high-school seniors. Since how we answer that question will affect the social mobility of millions of children, we need to ensure we get it right.

Illustration credit: Richard Lillash at City Journal