The number of reports of crop circles has substantially increased since the 1970s. There has been scant scientific study of them. Circles in the United Kingdom are not distributed randomly across the landscape but appear near roads, areas of medium to dense population, and cultural heritage monuments, such as Stonehenge or Avebury. In 1991, two hoaxers, Doug Bower and Dave Chorley, took credit for having created many circles throughout England after one of their circles was described by an investigator as impossible for human beings to make.