Bitcoin holders are those people who set the price for Bitcoin and everybody know that. "Whales" are paying the biggest role here, cause of every their move affect price a lot.
And if to talk about the price changing - I don't know how to predict it. Before I thought news and things that happening around crypto-currencies are making the price. But see, news from China dumped the price from 5000$ to 3000$ in September, but when South Korea followed this theme - the price become to grow! So there is no any stable way for prediction.
The news are the ones who make the price move and that is where you will base your prediction. If the news is bad then the market will go bad too and there will be a huge dumps in the price and that when the news is good then that is the opposite then the price will pump and people will make profit so if you want to predict and get a higher chance of being correct then go observe and read some news.