* Average of 54 normal and DRS overtakes per race in 2012  compared to 2011 season average of 43
* More normal overtaking in 2012: 68% compared to 2011 season average of 55%
* More normal overtaking than DRS overtaking at every race so far in 2012

Schumacher winter testing in his Mercedes in Barcelona, Spain 
For many years, a Grand Prix in Barcelona was synonymous with almost no overtaking  there were an average of just two overtaking moves per race between 2008 and 2010. That all changed last year: not only did 'normal' (i.e. nonDRS assisted) overtakes increase by a factor of ten  with a total of 22  but DRS enabled a further 29 overtakes, for a race total of 51; in other words, 25 times more than in the previous three years.
With much discussion about the most unpredictable start to a Formula One season for nearly 30 years, with four winners from as many races, and eight different drivers from six teams on the podium so far this season, has the composition of the racing changed materially compared to 2011?
How much overtaking have we seen in the first four races of the 2012 season?
The raw total for the number of passes the first four races of 2012 is remarkably similar to that from 2011  327 compared to 326 in 2011. This figure includes passes made because of damage, and those on cars from the three slowest teams, but does not include position changes on lap one.
How does the data compare when you drill down into more detail?
In 2011, there were a total of 220 normal and DRS overtakes in the first four races (NB: this figure does not include passes on the slowest three teams by faster cars); in 2012, there have been 215. However, in 2011, these were split 50:50 between normal and DRS overtakes in the first four races. In 2012, this split has been 68:32 in favor of normal overtaking. This compares to a season average from 2011 of 55:45 between normal and DRS overtaking, suggesting that the amount of normal overtaking has seen a significant proportional increase relative to last year.
Is DRS becoming less influential than it was last year?
In the first four races of 2011, there were two (China, Turkey) in which the number of DRS overtakes exceeded the total normal overtakes. Overall, there were eight of 19 races in 2011 at which DRS overtaking exceeded normal. So far in 2012, this has not occurred  in other words, there has been more normal overtaking than DRS overtaking at every race this year. However, it does not necessarily follow that DRS is becoming less influential; for example, even if a following driver does not pass in the DRS zone, the lap time advantage the DRS provides can help with conserving tires, or allow the strategic deployment of KERS elsewhere on the circuit to pass outside the DRS zone.
Has the overall amount of overtaking increased in 2012?
It is hard to say at this early stage. In 2011, the average number of normal and DRS overtakes per race was 43. So far, there have been on average 54 moves per race in 2012  a clear increase on 2011. However, by way of direct comparison, the first four races of 2011 saw an average of 55 moves.
Can any direct comparisons be made from circuit to circuit?
The most meaningful comparisons so far can be drawn from the races in Australia and China, which were run on the same circuits and in similar conditions both years. The 2011 season opener (the first race at which DRS was ever used) featured a total of 17 normal and DRS passes; in 2012, there was exactly twice as much passing  34 overtakes in total. What's more, although the 2012 race featured two DRS passing zones, this did not see a large relative increase in DRS assisted overtaking: DRS accounted for 30% of passing in 2011 and 35% of passing in 2012. In China last year, there were 67 normal and DRS overtakes  with normal overtakes accounting for 30 of them (45%). This year saw 69 passes, but 41 of them were normal overtakes (59%). The DRS zone remained identical to last year, but the race saw a significantly larger proportion of normal overtaking.
What should be expected in Barcelona?
Last year's race saw a total of 51 normal and DRS overtakes  above the season average of 43 moves. However, DRS overtakes accounted for 57% of these. It will be interesting to see if this is repeated, or whether the 2012 trend for a greater proportion of normal overtakes is maintained.