What single development item do you think made the most difference to a team's performance in 2015?
Dan Sainsbury, via email
Unusually for a Formula 1 season, there was no big new system thought up that everyone else needed to copy. So it was very much a year of teams converging on similar concepts.
Key among these is the front wing. Since the wings were narrowed in 2014, the endplate and cascade area has been constantly played with to manage the front tyre wake to clean up airflow downstream.