I sell many of these and generally have 4 or 5 available listings available that cater to this demand.  I think because I needed one myself, I have a better understanding of the ever increasing requirements.  We are the Sandwich Generation.   Another idea that is catching on is the Laneway House which is a small Granny Suite contained in its own little house in the back yard/lane.

Slight increase.

i read that article , which reminds me of agents losing opportunity on houzz.. but i digress... we see 3 generations OFTEN.. and the need for more single floor homes.. which puts pressure on land.. lot size..i feel a blog coming on

I haven't dealt with any in my entire career so can't help on these statistics.

Have not noticed much demand for this.