Costco's stock experienced a significant rally following the release of strong December sales figures. The company reported a 6.3% increase in U.S. comparable sales, with a two-year stacked growth exceeding 16%. Total sales for December rose 8.5% to $29.86 billion. Analysts, including UBS, reaffirmed positive ratings and price targets, citing consistent performance and investor confidence, with shares trading above their fair value.