Rising Yields Fatten Americans’ Pocketbooks

The summer bond-market rout is delivering a windfall to savers whose rush into higher-yielding investment products is reshaping the U.S. financial system.

Americans poured $36 billion into money-market funds in the latest week, taking advantage of yields that have soared past 5%— a figure that only recently seemed like a dream for consumers and businesses shopping for a place to park their cash. That marked the biggest weekly inflows since May, according to Refinitiv Lipper data through Aug. 16.

Assets in retail money-market funds have surged more than 25% this...