Since the global financial crisis a decade ago, a few simple guidelines have helped investors make sense of the markets.

Global growth and inflation will be perpetually weak. Central banks will help by keeping interest rates low. And stocks will almost invariably rise.

The rule book is now changing, a shift that is sending tremors through the financial markets. The Standard & Poor’s 500-stock index fell by more than 4 percent on Monday, deepening its losses from the previous week and erasing its gains for the year. The Dow Jones industrial average sank by 4.6 percent. Bond yields, the basis for key borrowing costs such as mortgage rates, have risen fast in recent weeks.