How does the observation of Ramadan affect the tourist industry in Turkey?

I don't really know, but I don't think it affects the tourist industry. Mainly because the touristic resorts are somewhat of enclaves and because it's in their best interest not to affect the tourist industry in any bad way...

From my experience of being a tourist in Turkia during ramadan is that it makes very little difference.   The main change that is observed is that traders stop everything at dusk so that they can break the fast - apart from that there doesn´t seem to be anything apparent.