It's an annual tradition in New York City: Each December, pedestrians fight for walking room on sidewalks populated by lush firs and frasers. Staffed by seasonal workers, these Christmas tree lots are often open 24 hours a day. We visited one of these tree stands on a sidewalk in West Harlem just after midnight to learn about the biz. But first, holiday season retail sales numbers out yesterday from the Census Bureau were unexpectedly flat.