In economics we can often observe the fact that a dependent variable is not always able to move immediately after a fortuitous change in an independentvariable.
"What has precipitated the change is an increasing concern over the very variable performance of exam boards, " said a spokesman for the Independent Schools Council information service (Iscis).
In his book about his career in policing, Sir Ian also condemned the Independent Police Complaints Commission (IPCC) for what he described as the "ridiculous delays" and "variable quality" of its inquiry into the 2005 shooting of Jean Charles de Menezes.