The coronavirus pandemic is emerging as an existential threat to the nation's small businesses. Already, economists project that more than 100,000 small businesses have shut permanently since the pandemic escalated in March, according to a study by researchers at the University of Illinois, Harvard Business School, Harvard University and the University of Chicago. Their latest data suggests at least 2 percent of small businesses are gone. The carnage has been even higher in the restaurant industry, where 3 percent of restaurant operators have gone out of business, according to the National Restaurant Association. Analysts warn this is only the beginning of the worst wave of small-business bankruptcies and closures since the Great Depression. "We are going to see a level of bankruptcy activity that nobody in business has seen in their lifetime," said James Hammond, chief executive of New Generation Research. "This will hit everyone, but it will be harder for small businesses." Many small-business owners say Congress' financial rescue isn't designed well to help very small businesses, known as micro firms, that have large overhead costs such as rent. "It wouldn't be surprising if well over 1 million of these micro firms ultimately fail," Mark Zandi, chief economist at Moody's Analytics, wrote in a recent note to clients, referring to firms with fewer than 10 employees.