[mumblemumble]

I suppose you can just pick the slowest 15% of days, then. If a price was randomly jacked up on a Tuesday, but nobody was around to buy it, was it really raised?

[maccard]

My bad, I misquoted [0] - section 1.2.2 says 28 consecutive days!

[0] https://www.legislation.gov.uk/uksi/2005/2705/schedules/made