OK, sorry I took so long, but I now have some real numbers.
I went go GSMArena, since they have the biggest mobile phone database I know if (3269 phones with Android alone, twice as much if you take all the OSs)
Here's what I found:
There were 499 Android phones made this year. Only 57 of them had screens smaller than 5". That's 11.5%
Then I took one step further, and filtered them by RAM. Unlike Windows Phone, Android eats 1GB of RAM like nothing, and it's a quite painful experience to switch between apps if you smartphone only has that. So I filtered out all the phones that have 1GB or less RAM. Here's what I got:
Out of 339 smartphones released this year, only 7 were smaller than 5". That is 2%.
Here's those 7 phones:
- Sony Xperia X Compact
- Cat S60 (not really compact - its body is as wide as a 5.5" phone, and thicker)
- YU Yunique Plus (I mean what? What is this brand? Does this even count?)
- Samsung Galaxy Xcover 3 (even with a 4.5" screen it's actually bigger than 5.1" Samsung Galaxy S7)
- Gionee W909 (not even available in Europe and the US)
- Coolpad Torino S (seems like this one is another cheap "quick disappointment" brand like Prestigio)
- Panasonic Eluga Arc (only available in India)
So basically the only viable option for a compact smartphone is the Sony, with Coolpad coming close, but still not having earned enough trust. That's quite sad.