What are the factors that affect the bitmex future price? How does the future price move in relation to the spot price?
Although I'm nit-picking, but the future price does not allows follow the exact same price movement of the spot price. Below, I a chart of the XRPU18 futures and the bittrex xrp price. The future went down significantly more than the spot price in the same time period.
Future price movements are much more drastical. It is caused by short/long liquidations due to overlavereged positions. Exchange is closing that position adding extra supply/demand what push price even more than spot price. After that price is going back where spot price is.
There is also separate supply and demand on futures and spot and price can be totally different. But most investors are looking on both price and doing their trades in way that those prices are quite the same. (if you see future price going down you know that spot price will go down too so you sell so price is actualy going down too but with big moves price can be different but only for short period)