Sorry, I should clarify! That's the NUMBER of ratings submitted, not the number of articles with those ratings! So, there are  3,389 5-star ratings, not  3389 articles with 5-stars.
But, the reason there are so many more 5-star ratings (not 5-star articles) is a combo of both of those factors you mentioned, but also that we tend to FEATURE and promote the best articles, so those get the most views / exposure, and then get the most # of ratings.
You asked 
	
		
	
	
		
		
			how many articles have 5 stars, how many have 4, etc.?
		
		
	 
Well, that's a tricky question depending on how we round the numbers... but if I use the sql query: 
"SELECT rating_avg, COUNT(rating_avg) AS average_count FROM `xf_nflj_ams_article` WHERE category_id IN (17,18,19,20) group by 
ROUND(rating_avg,1) ORDER BY `rating_avg` DESC"
we get:
		
		
	
	
... but if we change the "round" decimal_places to "0", we get: