Here's one for the exam files. From the Toronto Star:
The vices – smoking, drinking, sex – are usually bulletproof during a recession, says economist Perry Sadorsky, who teaches at York University's Schulich School of Business. So if the sex trade is hurting, "we are in the most serious depression since the 1930s. This shows the magnitude of the decline. It is deep and it is problematic."
Sex workers say their incomes began plummeting last fall, with johns pleading poverty and haggling over prices, and prostitutes bidding against each other.
"There are 60 people on the street, but they are all sex workers and there's no money for anybody," says Ray, who, like other prostitutes, did not want his real name used. "This economy is causing a lot of misery."
The following paragraphs suggests that the sex industry may have experienced a double-curve shift.
Sadorsky wonders if the economic crisis is forcing more people into sex work, thereby increasing competition on the street. Toronto police, who use a community complaints system to keep track of prostitution, report no increase in complaints, though they suggest this may mean sex workers are trolling in non-residential areas.
...The recession has seen the street price of oral sex, the most common service, plummet from $60 last fall to $20 today. "Full service" involving intercourse has dropped from $150 to $80.
A decrease in demand decreases price and quantity traded. An increase in supply decreases price and increases quantity traded. A simultaneous decrease in demand and increase in supply causes price to fall, but leads to an indeterminate change in quantity. This article provides anecdotal evidence consistent with this simultaneous change, at least on the street (the article goes on to mention escort services have experienced a decrease in their traffic, suggesting that a demand effect, um, dominates).