In only a year, the market value of office towers in Manhattan, home to the country’s two largest central business districts, has plummeted 25 percent, according to city projections released on Wednesday, contributing to an estimated $1 billion drop-off in property tax revenue. JPMorgan Chase, Ford Motor, Salesforce, Target and more are giving up expensive office space and others are considering doing so. Jamie Dimon, chief executive of JPMorgan Chase, the largest private sector employer in New York City, wrote in a letter to shareholders this week that remote work would “significantly reduce our need for real estate.” For every 100 employees, he said, his bank “may need seats for only 60 on average.”... Across the country, the vacancy rate for office buildings in city centers has steadily climbed over the past year to reach 16.4 percent, according to Cushman & Wakefield, the highest in about a decade. That number could climb further, even as vaccinations allow some people to go back to work, if companies keep giving up office space because of hybrid or fully remote work.