Table 1. Purely spatial high-risk clusters of tractor overturns in Kentucky, 1960–2002.

Type of cluster	Counties	Observed cases	Expected cases	Tractor Population	Annual cases/100,000 Tractors	Relative risk (RR)	p-Value	Log likelihood ratio
Most likely	Boone, Carroll, Gallatin, Grant	38	15.53	4531	19.5	2.55	0.00033	12.00
Secondary	Boyd, Carter, Elliott, Greenup, Johnson, Lawrence, Lewis, Martin, Morgan, Rowan	49	25.95	7569	15.1	1.97	0.00890	8.61

Note: The purely spatial analysis used a 10% spatial window and 19,999 Monte Carlo replications.

All 120 counties are included in the analysis.

The scan statistic scanned only for high-risk areas, and only significant clusters were reported.