Low risk:	PRFi < 30; PERI < 100
Moderate risk:	30 < PRFi < 50; 100 < PERI < 150
Considerable risk:	50 < PRFi < 100; 150 < PERI < 200
Very high risk:	100 < PRFi < 150; 200 < PERI < 300
Disastrous risk:	PRFi > 150; PERI > 300