View source for Second order efficiency

==History==
After Fisher (1922) introduced maximum likelihood as a general method of estimation of unknown parameters asserting that it provides estimators which are consistent and have least asymptotic variance, several papers appeared questioning Fisher’s claims.  Examples have been given of other methods of estimation which yield estimators with the same or better properties.  This motivated the author to make a deeper investigation of properties of estimators and methods of estimation.  In a series of papers, Rao (1960, 1961, 1962, 1963) introduced the concepts of Fisher consistency, which places a restriction on the estimating function, first order efficiency, correction for bias up to <math>O(1/n)\ .</math> These concepts bring out maximum likelihood estimates as having better properties than those obtained by other proposed methods.