Just a post before mine you were all gung ho to compare crime statistics between nations when you thought they said what you wanted them to say.
Looking at the numbers for England/Wales your statement about an increase in % reported is correct from 1981-1991, but then the report rate declined from then until 1999. In some cases the percentage being reported is below 1981 levels. You can find this data for each crime as probibility reported/offense.
EDIT: In fairness the number of reported assaults did shoot up in 1999. It does seem the efforts to not tolerate violence yielded some fruit. The tolerance for petty or non violent crimes is back where it was when the study began though.
The Coppers have been trying to get the number of unreported offenses down. Comparing reported crimes year-on-year is (IMO) extremely risky.
Which is why the British Crime Survey was set up