Costco Wholesale Corp COST reaffirmed its retail dominance, reporting an impressive 9.8% growth in December U.S. core sales. This result exceeded Wall Street’s 5.2% estimate and topped JPMorgan’s optimistic 6.7% forecast.JPMorgan analyst Christopher Horvers credited Costco's results to "market share gains, a shorter season, and a bit better consumer" working in tandem.E-commerce surged 35.7% year-over-year, partly thanks to Black Friday sales booked in December due to a holiday calendar shift.Meanwhile, int ...