1. Bitcoin supply and increasing/decreasing demand
2. Bitcoin in news: Influence of media on garnering negative and positive publicity
3.Bitcoin users and developers influence the rise and fall of price.
4.New technological changes to Bitcoin
For discussion for the above mentioned. You can check this link: https://hackernoon.com/factors-influencing-bitcoin-price-cfabdf634894
How about you? can you add more factor that can affect the price of the bitcoin? Comment below.
I think what you have listed up there is pretty enough and is the main reason why bitcoin keeps fluctuating all the time. Demand and supply has to be there and is something that applies to all kinds of assets in the world whether it is oil or bitcoin. Your second point about the news is one which covers every dam thing that is FUD's, news about specific country accepting and ignoring the crypto and much more and all these come to one point and that's moving the bitcoin prices up and down.
I don't believe there is average effect of how much volume is getting driven inward and outward the bitcoin market. The prices will change proportionally for it.