According to a report in The Times of 1 August 2013, only 50 crop circles appeared in July 2013, compared with more than 50 the previous year. And these circles are less elaborate than those of previous years. Crop circles first started attracting attention in fields, mostly of cereals and mostly in Wiltshire, in the late 1970s and were often attributed to supernatural forces or visiting aliens from distant planets. Later, in the autumn of 1991, two men demonstrated how they created crop circles using ‘tools such as rope, planks and step ladders’. The ‘circles’ became ever more elaborate.
Apparently the lack of circles in 2013 and their poor quality can be explained by the fact that most of their creators have retired or moved on to other activities.
See also: R. Vickery, A Dictionary of Plant-lore, 1995: 95.

Image: crop circle, unusually in Switzerland, July 2007, Jabberocky; Wiki Commons.