Conventional wisdom says that the weeks leading up to Christmas are the most important time of the year for retailers in the United States.

As Statista's Felix Richter details below, according to the National Retail Federation, Americans are going to spend between $979 and $989 billion during November and December this year, with average spending for gifts and other holiday-related items expected to amount to $902 per consumer.

But how reliant are retailers on a successful holiday season? Can two months really make or break an entire year?

Well, it depends.