Most Crimes of Violence and Property Hover at 30-Year Lows

…The department’s statistics differ markedly from those collected by police departments because they are based on a survey of United States residents and include crimes that were not reported.

In fact, only 48 percent of violent crimes and 38 percent of property crimes were reported, according to the report.

So…

um…

if 52% of violent crimes weren’t reported…

how do they know?