To add to this, high speed plans can skew the results. A few years ago, the maximum available speed in my area was around 16Mbps over ADSL. It's an old area that had old copper lines to most buildings. Lots of places were still on around 3Mbps. Fibre rollout had recently started, so pockets had gigabit speeds. Because they were in the same postcode area, all the speed checker sites started saying that the average for the area was 75Mbps.