Why should the terminal growth rate in a DCF never exceed long-run GDP growth?

The terminal growth rate cap is one of the most important guardrails in DCF valuation. The logic is mathematical, not just conventional wisdom.

The Mathematical Argument:

The Gordon growth terminal value formula is:

> TV = FCF_t+1 / (WACC - g)

This formula assumes the company grows at rate g forever. If g exceeds the growth rate of the economy, the company would eventually become larger than the entire economy — which is impossible.

Numerical Illustration — Crestline Software (fictional):

As g approaches WACC, the terminal value explodes toward infinity. At g = 7%, the terminal multiple is 50x — implying Crestline will compound at 7% forever, eventually dwarfing entire nations' GDP.

Why Fast-Growing Companies Still Get Capped:

Even if Crestline is growing at 25% today, the terminal value represents growth after the explicit forecast period — typically 10+ years out. By then:

1. The market will be more mature
2. Competition will have eroded margins
3. The law of large numbers makes rapid growth unsustainable
4. The company's growth rate must converge toward the economy's rate

Practical Guidelines:

• Developed markets: Terminal g = 2-3% (roughly inflation + real GDP)
• Emerging markets: Terminal g = 3-5% (higher nominal GDP)
• Never exceed: Long-run nominal GDP growth for the company's primary market
• Sanity check: If terminal value exceeds 75% of total DCF value, your growth rate may be too high

Exam Tip: The CFA exam tests this concept directly. If a vignette uses a terminal growth rate above GDP, that is likely the error you need to identify. Always justify your terminal g with reference to economic fundamentals.

Practice terminal value analysis in our CFA Level II question bank.