A method for measuring a change between two values for one or more data elements over time uses a “delta” value to indicate the significance of the change. The delta value is the difference between the two values, added to the ratio between those values multiplied by an asymptote. Experimental data sets with known values may be used to create data sets to which selection criteria are applied in order to calculate an optimal asymptote for the application of the delta values. This optimal asymptote may then be used for calculating delta values across an entire population for predictive purposes.