This thread has a lot of guessing what "normal" is for a sentence and time served in a situation like Paris Hilton's. This 
LA Times article has a lot of actual statistics.
One sentence sums it up pretty well:
	Quote:
	
	
		| Had Hilton left jail for good after four days, her stint behind bars would have been similar to those served by 60% of those inmates. | 
	
 Though is bears noting that her sentence and time served is not a complete outlier.