The United States -- the world's largest economy -- shrunk by 3.5 percent last year as the Covid-19 pandemic shut down large sectors of business and daily life, according to government data released Thursday. For the fourth quarter alone, GDP rebounded by an annual rate of 4.0 percent, the Commerce Department reported in its first estimate for the final three months of the year. Compared to the July-September period, the measure used in most other countries, fourth quarter growth was just 1.0 percent, the report said. hs/bgs