Hmm, not especially, where did you notice this? There are various abandoned buildings, but mostly in areas where people don't really want to live in, I haven't seen this being a significant issue, I don't think.

Whe I was in Greece I also saw a lot of buildings that seemed incomplete, often with apparently a floor missing. I was told it was something to do with tax and by not "completing" the building some tax was avoided.

Hmm, how do you mean a floor missing? Was the top floor half-built or something? I've never seen this that I can recall.

They had steel poles sticking up from the concrete. Essentially they looked like another floor was supposed to be added.

Ahh, I see. I feel like I've seen this in otherwise half-finished buildings, but not really in buildings that otherwise look complete, with people living in them, etc. Maybe I'm so used to it that I just don't notice it, though. I'll keep an eye out and report back!

I was driving to/from the coastal peninsula region southeast of the city starting at the airport

Oh hmm, were those buildings unused? I think that happens when they run out of money, mostly.