Does fashion trickle down from the rich or bubble up from the street?

Both, and perhaps neither. The classic answer is trickle-down: fashion flows from the upper classes to the lower, each class influenced by the one above. Two forces drive it. Lower groups imitate higher ones to claim status, and higher groups respond by adopting new fashions to differentiate themselves, which keeps the cycle moving. The German jurist Rudolf von Jhering probably developed the first full theory in 1883, and Georg Simmel described it in a 1904 article.

The challenger is bubble-up, or trickle-up, first described by Paul Blumberg in the 1970s: new trends are found on the streets and flow from lower classes upward. Blumberg wrote that in the last decade there had been more percolating up from the bottom than trickling down from the top. Think of the T-shirt, which Marlon Brando and James Dean redefined as legitimate outerwear and a deliberately rebellious statement, or of punk, which reached elegant gowns in 1977 when Zandra Rhodes added punk elements to them.

The dispute is not settled by picking a side. It is generally accepted among fashion researchers that fashions propagate more across social classes than they trickle down or up, because consumers tend to be more influenced by opinion leaders within their own social groups.