Srivastava estimation formalizes the introduction of additional prior
and posterior information in sampling to increase efficiency in estima
tion. An unbiased new estimator is given for Poisson sampling which is
approximately as efficient as the standard slightly biased estimator
without using any additional information. The increased efficiency pos
sible with this method or approximations to it are illustrated for Poi
sson sampling and point-Poisson sampling using simulations. Srivastava
estimation may be applicable in many forest inventory situations. Bes
ides efficiency, the seriousness of estimation bias and reliability of
variance estimators need to be considered in all applications.