Overtaking - how much, not enough, or too much of the 'wrong' sort - has been a frequent topic throughout the 2011 season, since the advent of DRS (the Drag Reduction System) and Pirelli tyres.

What is beyond all doubt is that the overall levels of overtaking have climbed to record levels - there have been nearly 1500 passes so far in 18 races.

However, no standard definition of an overtaking manoeuvre exists. The figures used below are calculated for strategic purposes, which are reflected in the categorisation, and compiled from a combination of video, timing data and GPS technology. Overtakes are classed as follows: Normal / DRS / Slow Cars (referring to HRT, Lotus, Virgin, as the strategic value of these overtakes is different) / Team-Mates (one driver can choose to let another pass) / Damage / Lap One.

So far, there have been 1436 overtaking manoeuvres in all categories. Excluding overtakes categorised as 'Lap One' or because of damage, there have been 1180 manoeuvres. The combined total of 'Normal' and 'DRS-assisted' moves - the indicator of what most observers consider to be 'clean' overtaking - is 804 overtakes. This gives an average of 45 normal and DRS overtakes per race.

There have been 441 normal overtakes this season and 363 DRS overtakes; from the total of 804 clean overtakes, 55% were normal and 45% were DRS. 300 overtakes were on the three slowest teams by faster cars, with passes between team-mates accounting for 76 overtakes.

The highest number of clean overtakes were recorded in Turkey (85), Canada (79) and China (67). The races with the fewest were Monaco (16), Australia (17) and India (18). Nine races featured fewer than 50 clean overtakes; eight races featured more than 50. There have been an average of 45 clean overtakes per race - broken down to 25 normal overtakes and 20 with DRS.

The highest ratio of DRS overtakes to normal, i.e. where the influence of DRS was greatest, were: Abu Dhabi (89%), Europe (81%), India (78%), Turkey (59%) and Spain (57%). The lowest ratio of DRS overtakes to normal were: Monaco (13%), Hungary (20%), Canada (22%), Japan (26%) and Great Britain (27%) - it should be noted that three of these five races featured wet or mixed conditions, and use of DRS was restricted for portions of the race in Canada and Great Britain. DRS overtakes have outnumbered normal moves in eight of 18 races.

In the first nine races of the season, there were on average 21 DRS overtakes per race - on average, 45% of clean overtakes. The influence of DRS has remained stable in the second nine races of the year: there were on average 20 DRS overtakes per race, representing on average 46% of clean overtakes.