And the winner of this Bitcoin price one year from now prediction contest is:
windjc
As of today's close (UTC), the 20 day SMA over USD/BTC on Bitstamp is 729.8.
Windjc's prediction was 650 to 750, so the actual (average) price is within windjc's prediction range.
The only other contestant who entered a range that includes the actual price is NorrisK (who entered 300 to 3,000). By the tie-breaking criterion stated in my OP, "narrower width of prediction range wins", windjc is the winner of the contest (100 < 2700).
Congratulations. You're a true market wizard, Harrywindjc!
Let me know which address you want me to send the funds to: 0.3 BTC pledged by myself, plus accumulated participation fees worth ~0.14 BTC (generously rounded up by several participants), for a total of ~0.44 BTC (~325 USD).
Cool. Nice bonus. I'll use this to pay for my Christmas present to myself - a hoverboard. So when I'm rolling around my house I'll think of all of you fondly.
Windjc 2016/17 tell us ur predictiion