I am currently at rank 21 and have invited 195 visitors.
I get 7 or 8 customers per day, for around a week now (which when substracted from 195 would make less then 150). The precise mechanics of the daily visitors is not quite clear to me, as one day I get more than another day. However, you will get more as you rank up (and with that invite more visitors).
The daily visitors will all appear at once when you enter Join Avenue for the first time that day (so all 7/8 come within one minute). For the rest of the day, if you do not connect with ither people, no other people will visit your Avenue. So I have no idea why you only get 4 a day, Nexus. Just maybe it might have to do with your "status", which might decrease when you recommend a wrong shop to a visitor. I would have to pay attention if I get more visitors after reaching 200 of them tomorrow.
Just if it matters: I have been visited by a total of 4 gym leaders (My brother only one). "Chain shopping" has only happened to me a total of 4 times, 2 of which left immediatly (while my brother, rank 19, has had it more then 30 times). Chain shopping is when visitors, after recommending a shop, go visit other shops in your avenue (up to visiting all of them once it seems), with all shops getting points, and only the highest of them increases the Join Avenue rank by that many points.
On a side note, non of Serebii's recieved points correspond with what I get. I always get 25% less than what Serebii has listed.