Going by last 5 seasons, and only counting races where numbers are listed all 5:
2009 - 185.315.000 viewers
2010 - 179.348.000 viewers
2011 - 186.348.000 viewers
2012 - 174.949.000 viewers
2013 - 175.561.000 viewers
So yes 2013 up from 2012 but last two seasons lowest viewership in past 5, and comparing 2009 to 2013 then it is a decline of 10 million sets of eyes, as we know that number of paying spectators have gone down as well, I have a hard time seeing the Chase adding anything to NASCAR which is worthwhile. And if anything then the move towards 'entertainment' over sport is what is costing them.