1. A method of predicting the health of a plurality of tools based on temporally ordered input data representing parameters indicative of tool health, the method comprising the steps of: using a sliding time window to partition the input data into temporally displaced data sets; using non-linear regression to determine, based on the data sets, a set of predictive values relating to tool health at a future time; and determining a tool-health metric based on one or more of the predictive values.