Beginning of 2015: ≈ 200 USD: It took 12 month for the price to double, Beginning of 2016 ≈ 430 USD, It took 12 month (Dec 2016) for the price to double -> ≈960 USD: It took 5 mont (May 2017) for the price to double -> ≈1800 USD: It took 3 month (Aug 2017) for the price to double -> ≈ 3600 USD: It took another 3 month (Nov 2017) for the price to double to 7200 USD.

My opinion: The price of Bitcoin will be at 14000 USD by February. At the End of the year the price for one Bitcoin could reach 25.000, I think.