Spot-checks on people already working in Australian child-related employment cane back with 30 records found.
They checked over 85,000 current workers. 0.000352941 hit ratio three ten-thousandths of one percent
That's the same as doing 85,000 searches in one county and getting 30 hits; or 8500 searches and getting 3 hits; or 2833 searches and getting 1 hit.