George gets a massage from a man and feels "it" move. Jerry asks him whether it was a "movement" of a "shift," as these are different. This scene can be compared to movements along versus shifts in demand and supply curves.
Hearing rumors that her birth control sponge has been pulled off the market, Elaine goes on a hunt for sponges based on the expectation of little future availability. Her demand has increased-she buys a case of sponges.
A seller of hula hoops finds that no one is purchasing his items, so he lowers the price in an attempt to increase demand. His price changes don't make a difference. When a boy finds a stray hula hoop and plays with it in front of his peers, all of the kids suddenly want one, and the hula hoop becomes a desireable product.