None of them are accurate! I tested them both, Terapeak and Marksight against my own sales and they are always and forever off! Hard to buy into a service that doesn't reflect my own sales! Anyway if you want to know sell through rate take the number of sold listings and divide it by the number of ended listings. You can get a slight idea there, but even that is not accurate since we sellers regularly close listings early and relist as similar to make Cassini happy.