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.