Reminds of the Just-noticeable-difference concept (http://en.wikipedia.org/wiki/Just_noticeable_difference http://en.wikipedia.org/wiki/Just_noticeable_differen

Reminds of the Just-noticeable-difference concept (http://en.wikipedia.org/wiki/Just_noticeable_difference http://en.wikipedia.org/wiki/Just_noticeable_difference) from psychophysics. If disorder is evaluated as a general aggregate of cleanliness, crime etc. An increased baseline of disorder will mean that any personal transgressions that were perceived as "wrong" before would now be perceived as lesser wrongs in comparison. They probably accounted for this, but is it possible that graffiti is resulting in bikers park elsewhere, implying that it isn't individual behavior that is being modified, but group make-up.