Sources of advantage
Switching costs, network, scale, intangible assets and structurally lower costs are different mechanisms. Ask who pays, why it doesn't change and what prevents copying. A high fee is a result, not a sufficient explanation.
Financial evidence
Look for persistent margin and return on equity, retention, pricing power and growth without disproportionate investment. ROIC compares after-tax operating profit with required capital; must exceed the cost of capital during a cycle.
Example
Two companies grow 15%. One needs to reinvest 80 of every 100 of profit; another, 25. The second can distribute more cash or grow with less financing.
Reinvestment
A great business creates more value when it can still reinvest at high returns. Without opportunities, accumulating cash or purchasing expensive products reduces quality. Evaluates potential market and discipline of the management team.
How it erodes
Technology, regulation, new channels or dependence on a platform can reduce the advantage. Defines leading indicators: churn, price, quota, acquisition cost or incremental margin.