Black Friday evolves but still marks start of holiday shopping season

The holiday shopping season kicks off on Friday with traditional Black Friday sales, though many retailers got a jump on the competition by getting started with deep discounts on Thanksgiving Day, and analysts forecast data to show that online shoppers spent a record $4 billion on Thanksgiving, MarketWatch reports. The total had already reached $2.1 billion as of 5 p.m. Thursday, a 20.2 percent increase compared to the same point last year. Demand was so high on Thursday that Costco's website and app were briefly hampered by heavy traffic, USA Today reports.

Black Friday is continuing to evolve, as many stores try to snag a bigger share of holiday sales by cutting prices days or even weeks before what used to be a one-day shopping frenzy. Shoppers are expected to spend up to $731 billion in November and December, roughly 4 percent more than in the same period last year.