Here's an article from the Wall Street Journal, via Yahoo Finance, so it's free:
High Schoolers Feel the Chill In the Hunt for Summer Jobs Wall Street Journal Wednesday April 23, 2:39 pm ET By Sue Shellenbarger
More teens will be looking for summer jobs this year than last — but fewer will be getting them.
After sinking to a new low in 2007, teen summer employment is expected to fall again, to the lowest rate in the 60-year history of government jobs data. Working teens ages 16 to 19 will slide to 34% of the population, from 34.5% last year, predicts of the Center for Labor Market Studies at Northeastern University. That's down from 45% in 2000 and a high of 48.5% in 1989.[More]
Of course, the biggest reason for this is immigration. See New York’s Other New Economy By William Fronhoefer, or Joe Guzzardi's Abolishing New England: Cheap Labor vs. College Kids..
Ms. Shellenbarger does mention the I-word as one factor:
Weakness in the economy is accelerating a structural shift in employment patterns. More adults, including unemployed college grads, older workers, former welfare recipients, immigrants and working adults seeking second jobs, are competing for low-skilled hourly posts.
But immigration is the largest factor—there are uncounted millions of illegals in the country. I say uncounted, because they can't be counted, but it's something like twenty million.