The buying nudge

Black Friday prompts us to buy more.

Temporary discounts instill a fear of missing out on deals.

Fast, free shipping and easy returns make online shopping convenient.

Amazon's clever nudge has been to extend the return period for end-of-year purchases until February 6, exactly one month after Three Kings' Day, the Spanish equivalent of December 25th's Santa Claus.

If anything, Black Friday is harvest time for those who wait and save.