As for the peak seen in 2009, it can be partly explained by the murder of approximately 30 journalists in only one day, in an ambush in the Philippines on 23 November 2009.

UNESCO: MEDIA SERVICES

Or can it be explained by a new force--rapidly rising prosperity around the world?

FORBES: Trillion-Dollar Question, Part II

"It's not something that can be explained by modern science, " he says.

WSJ: Radiation Worries Spur 'Quackery' Cures

As more data have become available, however, it is becoming clear that the difference can be explained largely by seasonal fluctuations.

ECONOMIST: The science