Buffett and Clark's premise is that given a company's last 11 years of earnings and dividends, the historic-low price-to-earnings (P/E ratio) data point, and a company with a track record of consistent earnings growth over time (which suggests a durable competitive advantage), an investor can produce a conservative estimate of the company's future stock value and return on investment.
With a financial calculator, the valuation process is six steps. The authors don't number the steps but if you count the number of calculations to arrive at the forecasted value in 10 years, it is six. These calculations are addition and multiplication, and basic time value of money functions: present value (PV), future value (FV), number of compounding periods in years (N), and interest rate (I/Y).
Some reviews noted the repetitiveness because Buffett and Clark go over this six step calculation process 17 times using different companies in Warren Buffet's portfolio; however, the repetitiveness is worthwhile because they published in 2011, estimated 2021 stock values for 17 companies, and now that 2021 has passed we can see how accurate their process is.
What you'll see is that an equally-weighted portfolio (where you invest an equal dollar amount in each company) produces an estimated 2021 return that is close to the actual 2021 return.
Endnotes:
* You have to diversify because there's a lot of variance in actual return vs. expected return. Some companies' actual returns significantly underperfomed the projections: GlaxoSmithKline (-68%), Coca-Cola (-65%), ConocoPhillips (-64%), and Wells Fargo (-57%), while others significantly outperformed: Costco (+231%) and Moody's (130%).
* The stock market's all-time high to-date was December 2021. Buffett and Clark's 2021 estimates would have been overly optimistic had the market not peaked at the right time.
* This actively managed portfolio of stocks selected by Warren Buffett underperformed the S&P 500, a passive index which had an annualized returned of 16% over the decade.