I too have a two listings. Although, I have only been hosting a couple of months now.
I have had 9 guest on one listing and 1 on the other. To add to the mystery on the statistics tab my least popular listing shows no views.
After a bit of investigation I've found many guests are filtering out the least popular listing. EG my popular listing accommodates 4 guests and has two beds. In fact, the guests I quizzed didn't even realise I had two listings. I also only have instant book on the more popular listing so airbnb favours this listing. I did drop the price on the less popular to a ridiculously low amount with no effect so its not the price. Still just bookings on the more popular listing.