The ratio of decay constants ƒB/ƒD

The result ƒ_B≈ƒ_D which had been obtained from sum rules and lattice calculations, and which contradicts the naïve prediction ƒ_p1/√M_p, is rederived using a simple argument based on semilocal parton-hadron duality. Is is argued that both here and in sum rules the key point is the use of semilocal duality instead of the bound-state wave functions.