yet I don't see any huge drops around December 2015 (between 2015-11-02 and 2015-11-09 it went from $501 to $297 but back then this was still considered "normal" I suppose).
It's more "normal" back then because volatility was expectedly very high, but it's pretty much the same today. Liquidity might got higher, but it's still almost just as volatile.
One thing you should remember: regardless how much bitcoin is being generated per block, heck, it could be .01 BTC per block, but if there isn't enough demand to clear off the sell offers on exchanges, don't really expect a price rise. Though supply is definitely a huge factor, demand is still the biggest factor.
Volatility remains one of the best known hallmarks of Bitcoin and what we are experiencing these past few days are very much manifestation of this characteristic. There are a lot of ideas and speculations as to what really triggered this recent slump but for me it is all about demand and supply. Let's hope that the pullback is in fact a preparation for a good bull run in 2020. It would be interested how Bitcoin will eventually close its price this December but for sure there is a slim chance of a "moon" type run in the remaining months of 2019.