Power of compounding

The power comes first, in three exhibits.

What does compounding do over the long run?

Back-loading. ₹1 compounding at 12% is worth ₹3.11 after 10 years, ₹9.65 after 20, ₹29.96 after 30 and ₹93.05 after 40. The decades contribute +2.11, +6.54, +20.31, +63.09. The fourth decade adds thirty times what the first did, at the same rate. Compounding pays almost all its wages at the end. That makes interrupting it (panic-selling, dipping into the corpus, forced liquidation) so expensive, and it's why "time in" beats "timing" as a default posture. The classic human exhibit is Warren Buffett, the overwhelming majority of whose wealth arrived after his 50th birthday (commonly cited from his disclosed net-worth history; check the current figure, since the point is the shape and the decimal matters less).

Small edges, huge terminal gaps. 12% for 30 years multiplies money 29.96×, and 15% does 66.2×, so three extra points more than double the terminal outcome. This cuts both ways.

Costs compound too. A 100 bp annual fee on a 12% gross return, which nets 11%, turns 30-year wealth from 29.96× into 22.89×. So the "one percent" consumed 24% of the terminal outcome. That's a lot to lose to something called one percent. Every basis point of recurring cost is a permanent passenger on your compounding train. It's the same arithmetic behind Phase 2's obsession with ROIC durability. A business compounding capital at 20% against 12% for two decades is 1.20²⁰/1.12²⁰ = 3.97× better, which is a long way from "8 points better."

The SIP arithmetic. India's favourite investing habit is a monthly investment A for n months at monthly rate r_m, which grows to:

FV = A × [((1 + r_m)^n − 1) / r_m]

Take ₹10,000 monthly for 20 years at 1% per month, the common calculator convention for "12%". Note that 1% monthly is really 12.68% EAR. FV = 10,000 × [(1.01²⁴⁰ − 1)/0.01] = 10,000 × 989.3 = ₹98.9 lakh, on ₹24 lakh contributed. Now apply the real-versus-nominal ruler. At 5% inflation, that's 98.9/2.653 = ₹37.3 lakh in today's rupees. It's still excellent and comfortably ahead of the ₹24 lakh you put in, but it's a third of the sticker number. Bad financial marketing sells the sticker without the deflator. You now know better.

What are the limits of compounding?

Then the limits, and there are four of them.

1. The average hides the path. This is your first look at sequence risk. For a lump sum with no additions or withdrawals, the order of returns is irrelevant. 0.75 × 1.10 × 1.30 = 1.0725 in any order, because multiplication commutes. The moment money flows in or out, order matters enormously. A retiree withdrawing a fixed sum is hurt worst by bad years early, since each withdrawal locks in the damage. A SIP accumulator is helped by bad years early, since contributions buy cheap. Worked example 3 computes both on the same return set. The full treatment, covering safe withdrawal, cash buffers, and why "average return 12%" can still ruin a retiree, is Phase 9's. For now, carry this much: compounding maths uses one number, life delivers a sequence, and with cash flows the sequence is destiny.
2. Volatility drag, quantified. Steady 6% for two years gives 1.06² = 1.1236. "Average 10%" delivered as +40% then −20% gives 1.40 × 0.80 = 1.12. The calmer fund wins with a four-point-lower arithmetic average. So judge multi-year records by the geometric CAGR, never by the arithmetic mean of yearly returns. The gap between the two measures the volatility drag.
3. The engine must survive the whole runway. Projecting 15% for 25 years assumes a business, or an investor, that keeps earning reinvestment opportunities at that spread for 25 years. Almost nothing does. Competition arrives, markets saturate, returns mean-revert. That's why the market pays so much for the rare durable compounder, and it's why Phase 4 exists, since moats are what defend a reinvestment rate. Damodaran's data and Mauboussin's base-rate work, anchors for Phases 3 and 4, show that sustained 20%+ growers are a tiny minority of large firms. When someone says "just compound at 18%," ask them what defends the 18% in year 14?
4. Inflation compounds against you, in parallel. Every nominal projection carries a shadow projection of the price level. At Indian inflation, 25-year nominal numbers roughly triple-count purchasing power, since 1.05²⁵ ≈ 3.4. Always run the deflator.

How does compounding link to ROIC and the cost of capital?

This ties back to the programme's spine. The five questions ask whether a business earns ROIC above its cost of capital and can reinvest at that spread. You can now read that sentence as numbers. ROIC is the business's compounding rate. The cost of capital is the rate stack the providers of money demand for waiting, inflation and doubt. Reinvestment is what turns a good year into an exponent. A company reinvesting at 20% against a 12% hurdle is 1.20^t racing 1.12^t, and everything in Phases 2–5 is machinery for judging whether that exponent is real and how long it can run.