How accurate are the MGM2 estimates?
Short answer: Figure errors of 10-20% if the input choices/data are reasonable. Longer answer: Accuracy of the estimates rests largely on the accuracy of the model inputs (GIGO) – that is visits, segment shares, spending averages and multipliers. Our experience is that the largest errors are usually due to the visit data. Next in importance are the spending averages if they don’t accurately reflect your visitors. Multipliers mostly affect the estimates of the secondary effects and if properly chosen are the least important source of errors. The NPS Park visit estimation protocols are some of the best of any resource management agency (thanks to Butch Street), but counting visitors is inherently messy and MGM2 requires additional information to sort out park re-entries, determine days/nights spent in the local area, and estimate segment shares. If the spending averages come from your own park visitor survey, then sampling errors for the study provide an estimate of one source or error.