Econometrics may be defined as the quantitative analysis of actual economic phenomena based on the concurrent development of theory and observation, … - Richard Stone

In 1945, the war ended and I was chosen to be the first director of the newly-established Department of Applied Economics in Cambridge. Between leaving the government service and taking up my new post, I had a break of about three months which I spent at the Institute of Advanced Study in Princeton. I intended to use my time there writing up my ideas on a social accounting system for the measurement of economic flows, a thing I had wanted to do for years but had not had time for during the war. What happened was that, in Princeton, I met , the Director of Intelligence at the League of Nations, who wanted a paper on the problems of defining and measuring the national income and related totals for consideration by the League's Committee of Statistical Experts. He asked me if I would undertake the work and naturally I accepted. I soon had a memorandum ready and it was discussed in Princeton while I was still there by a subcommittee convened by Loveday. Their report was eventually published by the United Nations in Geneva in 1947 under the title, Measurement of National Income and the Construction of Social Accounts, with my memorandum as an appendix.

In the second place, a system would involve more variables than those which may be supposed to enter into demand relationships, and so the preliminary work of estimating the necessary time series would also be increased. In the third place, in the simultaneous method of estimation the estimates of the original parameters come to depend on most of the remaining estimates, and so it is quite likely that they will have large sampling variances.

There is no hope, as far as I can see, of pushing the postulates of economic theory back to a set of irreducible axioms.