U.S. life expectancy inched up last year, but could decline in 2020 by the largest amount since World War II, as COVID-19 becomes the nation’s third-leading cause of death. Data released by the Centers for Disease Control and Prevention showed that life expectancy rose to 78.8 years in 2019, an increase of one-tenth of a year. But the gain will be erased by a large drop in longevity when the government releases 2020 figures next year.