Appendix H — Personal Finance Primer

The economics you need for your own financial life, distilled from the textbook.

H.1 The five rules of personal finance (from the textbook)

Rule 1 — Start saving early. Compounding is the most powerful force in finance (Rule of 70, Chapter 25). $200/month at 7% from age 22 = ~$550,000 at age 65. Starting at 32 = ~$260,000. Ten years of delay costs you half.

Rule 2 — Diversify. Don't put all your money in one stock, one sector, or one asset class. A diversified index fund (S&P 500, total stock market, or target-date fund) gives you broad exposure at minimal risk and minimal cost. (Chapter 28)

Rule 3 — Keep fees low. The difference between a 0.05% fee (Vanguard index fund) and a 1.0% fee (typical actively managed fund) is enormous over decades. On a $500,000 portfolio, 1% fees cost you about $5,000/year — every year, forever. Most active funds underperform index funds anyway. (Chapter 28)

Rule 4 — Understand opportunity cost. Every dollar you spend is a dollar you can't save. Every hour you work is an hour you can't spend with family. Make these tradeoffs consciously. (Chapter 1)

Rule 5 — Beware behavioral traps. Present bias makes you spend now instead of saving. Loss aversion makes you hold losing investments. Anchoring makes you pay more than things are worth because of the "original price." Sunk-cost fallacy makes you throw good money after bad. Knowing these traps doesn't make you immune, but it helps. (Chapter 10)

H.2 The big financial decisions

College. Apply the cost-benefit framework from Chapters 1 and 36. Total cost = tuition + foregone wages. Average benefit = ~$1.2M lifetime earnings premium. But variance is huge — field, school, and completion matter enormously. Don't borrow more than your expected first-year salary.

Student debt. Median: ~$30K. Federal loans have income-driven repayment options. Prioritize paying off high-interest private loans. Don't default — the consequences are severe and permanent.

Housing. Renting is not "throwing money away." The decision depends on: how long you'll stay (buying makes more sense for 5+ years), local price-to-rent ratios, mortgage rates, and your financial flexibility. Apply supply-and-demand (Chapter 5) to understand your local market.

Retirement. Enroll in your employer's 401(k) immediately (Chapter 10 — auto-enrollment nudge). Contribute at least enough to get the employer match (it's free money). Use a target-date fund if you don't want to think about asset allocation. Increase your contribution by 1% each year.

Insurance. Health insurance is essential (Chapter 14). Beyond that: insure against catastrophic losses (health, liability, disability) but not small losses (extended warranties are almost always bad deals — the expected payout is less than the premium).

H.3 The one chart you need

   Your net worth
   over time          ╱╱
                    ╱╱
                  ╱╱
                ╱╱   ← With consistent saving + compounding
              ╱╱
            ╱╱
          ╱╱
        ╱╱
      ╱╱
    ╱╱_______________ ← Without saving
   ╱╱
   |________________________________
   22    30    40    50    60    65    Age

Start early. Be consistent. Let compounding work. The rest is details.