There is one popular theory spread among thoroughbred buyers at public auctions that younger mares’ progeny, at their birth ranks 2-3, usually are born with better body conditions, also have a higher chance to succeed in their future racing careers and therefore are sold at higher price. So our interest is to test this hypothesis, we examined the impact of dam’s age and the progeny’s birth rank on hammer price in a hedonic pricing model to test the significance of its coefficient; Using the same model, we change the dependent variable to these yearlings’ future earnings on race tracks, to see whether the same explanatory variables have a similar impact on horses’ racing performance. With discovering the magnitude of marginal values of each characteristic in two equations, we compare the results especially of the variables represent dam’s age and parity. Our goal is to help buyers and sellers of thoroughbred yearlings to further understand price discovery and provide more statistical information to help them make reasonable and better purchasing decisions; information on how birth rank and dam’s age impact progeny’s future performances is important for both buyers and sellers, for the reason that if we prove these factors are not playing a significant role in their future performances, reasonable buyers will not neither base their purchasing decisions on the dam’s age nor the birth rank of the progeny.