The idea. A moat's worth is the extra years of ROIC−WACC spread it protects. Mauboussin named this duration the CAP with Paul Johnson in 1997, in "Competitive Advantage Period: The Neglected Value Driver." It's the period over which a company is expected to earn returns on incremental and existing capital above its cost of capital. After that, competition, the default state of the universe, grinds the spread to zero and growth stops adding value. Your iron rule from the cost-of-capital work still holds: growth at ROIC = WACC is worthless. That makes the CAP the bridge from moat judgment to your Phase 3 machinery. It's also the number your reverse DCF was silently solving for when it asked "how long must the good times last to justify this price?"
What is the competitive advantage period formula?
The valuation skeleton (Miller–Modigliani, 1961). Any firm's value splits into two parts: what the current business is worth if it never improves, plus the value of future value-creating investment:
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Value = NOPAT / WACC + [ I × (ROIC − WACC) × CAP ] / [ WACC × (1 + WACC) ]
where NOPAT = normalised current net operating profit after tax, I = the annual net new investment the firm can deploy, ROIC = the return on that incremental investment, and CAP = the number of years such positive-spread investment remains available. The first term is the steady-state value from your reverse-DCF work, the same EV ≈ NOPAT/WACC you met as the whole value of a no-barrier firm. The second is franchise value, and look at what multiplies it. There's the spread, and there's the reinvestment, because a spread with nothing to reinvest earns applause and no value (efficient-scale niches from the first moat module often end up here). And there are the years. Respect the simplifications. This formula holds I and the spread constant during the CAP and drops excess returns to zero afterwards. It's a step function standing in for the gradual fade real companies go through. Treat it as the teaching skeleton, and use the reverse-DCF engine with an explicit fade schedule as the production tool.
Worked example: how the CAP changes value
Worked skeleton (synthetic). NOPAT ₹1,000 crore, WACC 12%, incremental ROIC 25% and reinvestment of 40% of NOPAT give I = ₹400 crore/yr. Growth is then ≈ 40% × 25% = 10%, from the g = RR × ROIC you met with returns on capital.
- Steady-state value = 1,000 / 0.12 = ₹8,333 crore.
- Each CAP year adds 400 × (0.25 − 0.12) / (0.12 × 1.12) = 52 / 0.1344 = ≈ ₹387 crore of value.
- The multiple is the CAP in disguise:
| CAP granted | 0 yrs | 5 yrs | 10 yrs | 15 yrs | 20 yrs |
|---|---|---|---|---|---|
| Enterprise value (₹ cr) | 8,333 | 10,268 | 12,202 | 14,137 | 16,071 |
| EV / NOPAT | 8.3× | 10.3× | 12.2× | 14.1× | 16.1× |
Read that table twice, because it reorganises everything you learned about multiples when you built DCFs. A multiple is a moat-duration claim. When two similar-growth firms trade at 10× and 16× NOPAT, the market isn't confused. It's granting one a five-year CAP and the other twenty. Your job is to decide whether the evidence, meaning the share tables and Helmer's gates, supports the grant.
How do you read the market's CAP?
Reading the market's CAP (the implied-CAP inversion). Run the skeleton backwards: implied CAP = (EV_market − NOPAT/WACC) / value-per-CAP-year. Say the synthetic firm above trades at EV ₹14,000 crore. Then implied CAP = (14,000 − 8,333) / 387 ≈ 14.6 years. Now the moat conversation has a falsifiable form. The price asserts ~15 years of a 13-point spread reinvested at ₹400 crore a year. Do the four lenses support that? It's your reverse DCF with the duration lever isolated. In production, prefer the full reverse DCF with a fade schedule, where the spread erodes linearly or geometrically to zero. That's because the step-function skeleton overstates CAP for low-reinvestment firms, whose true "I" includes brand and R&D spending buried in the P&L. Capitalisation adjustments from your earnings-quality work fix this, and Worked Example 2 shows the distortion live.
How long should a CAP be?
Calibrating N: base rates before stories. Everything you know about mean reversion applies to the CAP with full force. Your transition matrices from the returns work (about half of top-quintile ROIC firms are no longer top-two-quintile a decade later) and Mauboussin's Base Rate Book both say the default fade is fast. ROIC distributions you built when benchmarking say persistent 20-year spreads are a small minority of all listed firms. Here are some practical calibration bands. They're rules of thumb and not laws, so argue from the evidence in your dossier.
- No-barrier operators: CAP ≈ 0 to 3 years, steady-state value only.
- Single, perishable advantages, such as supply-side tech leads, unpriced regulation, one non-interlocked power: ~3 to 7 years.
- Gated multi-power stacks with confirming share tables: ~10 to 15 years.
- Interlocked scale-plus-captivity with 20+ years of demonstrated stability (think of the paints and cola specimens): 15 to 20+, granted grudgingly.
Market-implied CAPs computed across large markets typically average around a decade, with enormous dispersion. They run from zero for deep cyclicals at the peak to 30+ for elite franchises. So a price implying 25+ years asserts that the company belongs to a club whose historical membership is tiny. Respect two asymmetries. High spreads fade faster than modest ones, because bigger advertisements attract bigger armies. And demand-plus-scale moats outlive supply moats, as Greenwald's perishability ranking said. There's one limit to admit, too. A CAP is a judgment expressed in years, and it isn't a measurement. It beats "wide moat" because it's falsifiable. A 15-year CAP claim tells you which future share tables and incremental-ROIC prints would prove it wrong, and the erosion lens teaches you to watch them.