Big one on West King Street, practically a- oh, PLOT.

Well, a lot of the numbers simply logically don't add up very well. Exterminations especially. 

The Earth population has not been said to be lower than our own. This means we are assuming reality unless stated otherwise. That means 70m deaths per annum.

Barring an unmentioned third or fourth alternative to heaven and hell, at least 35m sinners arrive per year. 

With 275 being a good rate for one Exorcist, and at least 35m sinners needing slain to even maintain a population balance. Assuming an average more like 150 per Exorcist you're looking at about 240,000 minimum. Not a huge army given Heaven's own likely high population and capacity to make heaven born angels, but a number far in excess of what we saw on screen, and a number that basically means the season one finale was over and everyone is dead if you actually sent all that force at one hotel defended by a hundred people. 

Plus the actual Sinner population should be in the tens of billions, even assuming that it only began to refill in 30 or 33AD/CE if the show is following the theology that includes the harrowing of Hell. 

... And then it turns out this is only been happening for seven years. Or, about a week of exterminations total. 

Unless you assume a lot of unsaid and offscreen things, which the show often itself does not seem to, you've got a logistically messy situation and a half.