I believe the rating is the percentage of total TV audience.  If there were fewer people watching all TV programs last year, you could have a higher rating for the Cup race but fewer people watching the race.  
Think of it as a slightly bigger slice of a slightly smaller pie, giving you less pie overall even though the slice is larger.
				
			Think of it as a slightly bigger slice of a slightly smaller pie, giving you less pie overall even though the slice is larger.
 
	 
					
				 
					
				 
					
				 
					
				 
					
				 
					
				