Warren E. Buffett took aim on Saturday at the “negative drumbeat” of this year’s presidential campaign, saying that the view that children today would not live as well as their parents was “dead wrong.”

In his annual letter to shareholders, the billionaire investor — who has endorsed Hillary Clinton for president — wrote that “the babies being born in America today are the luckiest crop in history.”

Employing his typical folksy humor and optimism, Mr. Buffett’s letter discussed such themes as income inequality, climate change, efficiency and prosperity, as well as investments like BNSF Railway and Kraft Heinz.

“For 240 years it’s been a terrible mistake to bet against America, and now is no time to start,” he wrote. “America’s golden goose of commerce and innovation will continue to lay more and larger eggs.”