  We investigate effects of threshold resummation of logarithmic corrections
$\ln N$ in Mellin space quantitatively. Threshold resummation leads to
enhancement of next-to-leading-order QCD predictions for jet production at
large jet transverse energy, which is in the trend indicated by experimental
data. We show that this enhancement is completely determined by the behavior of
threshold resummation at small $N$, the region where hierachy among different
powers of $\ln N$ is lost and current next-to-leading-logarithm resummation is
not reliable. Our analysis indicates that more accurate threshold resummation
formalism should be developed in order to obtain convincing predictions.
