PayPal Holdings, Inc. (PYPL)

Income is a share of every amount processed. The key metrics are total payment volume and how much of it the company keeps: the second has declined for years under competitive pressure, and volume growth does not always offset it.

Beyond the core brand the company owns Venmo — peer-to-peer transfers with a strong position among younger users — and Braintree, payment processing for large merchants. Braintree brings large volume at low margin, and a revenue shift toward it is precisely what dilutes overall profitability.

Competition is dense on every side: Apple and Google with their wallets, Stripe and Adyen in processing, and retailers' own checkout buttons. The company has cut costs and begun buying back stock; it pays no dividend.