The 2021 holiday shopping season has gotten off to a slow start, with retail sales cooling in November as consumer spending decreased. Experts are still relatively optimistic about the season, however.

Retail sales stumbled in November, according to the U.S. Census Bureau. Retail recovery slowed to 0.3%, compared to the revised figure of 1.8% for October. Compared to last year, sales are still considerably improved, coming in 18.2% above November 2020.

The coronavirus pandemic continues to weigh heavily on retail sales. Much like the initial surge of the Delta variant, Omicron has caused a drop in shopping at brick-and-mortar stores.

Supply line dysfunction continues to leave shelves partially or completely barren at major retailers such as Target (TGT  ) and Walmart (WMT  ). Customers of Amazon (AMZN  ) continue to experience lengthy shipping times as the retail giant struggles to keep pace.

In addition, rising inflation continues to pressure Americans. The Federal Reserve shifting its language away from "transitory inflation" came well after consumers suffered rising gas, food, and material good prices.

Another drag on retail sales may be the staggered sales that some retailers have held this year. Black Friday and Cyber Monday sales slumped after many consumers took advantage of early sales in October and earlier.

In general, consumers appear to be shifting preferences towards earlier shopping.

"If you look at the weakness in November sales, it looks more related to holiday shopping," Aditya Bhave of the Bank of America (BAC  ) told the Wall Street Journal. "Some of that is going to be a reflection of prices, but the bigger story here is the change in the seasonal pattern."

Some experts are still somewhat optimistic for December. One firm has written that the season is a "marathon, not a sprint."

Industry trade group the National Retail Federation expects retail sales in November and December to grow between 8.5% and 10.5% this year, compared to the last year, to total up to $859 billion.