How much faster have Formula 1 races gotten since 1950?

Formula 1 is considered to be the most historical and competitive racing leagues from around the world. Each year, it seems as if the cars get faster and faster. I am curious to see how much faster cars of gotten at historical tracks.

Tracks

Great Britain

Since 1950, the races at Silverstone have gotten remarkably quicker. Yet, in recent years, it has appeared to be much slower. Those slower races can be attributed to poor weather, which makes the track conditions less driveable and much slower.

Monaco

Starting in 1980, cars do not appear to get any faster at Monaco. Monaco is a very famous street circuit, yet times are difficult to improve as the roads are old and narrow, and they have not gotten bigger as F1 cars have gotten bigger.

Italy

There is an obvious decrease in time from 1950-2000. It is really surprising to see that cars have not gotten that much faster at Italy since 2000.