Where have all the goals gone?

Good analysis of how conditions, like which football is used, altitude of location, are affecting how many goals are scored in this World Cup...
http://beta.thehindu.com/sport/football/article467891.ece
Excerpts:

The question then is why. Many have blamed the ball. Many anticipated it would be difficult for goalkeepers, but outfielders seem to find it difficult to control.

Figures are hard to come by, but several players have complained about its tendency to fly without dip, and observational evidence suggests a lot of shots blasted over and a lot of overhit crosses.
...

Then again, that may be the fault of the altitude — thinner air means fewer molecules to generate friction, and thus spin is diminished — which may also explain the tendency for crosses and shots to be overhit.