799. Harrod to J. M. Keynes , 3 August 1938 [a]
[Replies to 791 , followed by 801 , answered by 806 )
Garrards Farm, Uffington, Berks. [b]
3 August 1938
Owing to the incompetence of the post office, I did not get your letter until 2 weeks after it was delivered. It is always safer to write to Christ Church.
I very much hope that we shall see you in Cambridge. But perhaps I ought not to say that, since you must not think of coming, if it is likely to be any impediment to the slow process of recovery. We can get Champernowne or someone [c] to read out your paper. 
I think Tinbergen is well aware of the limited validity of the numerical co-efficients he introduces into his equations. But if after working out his equations for a number of different countries and places, he finds that certain influences, which theory deems to be present, are consistently small compared with other influences--which must also of course be justified by theory--, this must and ought to modify the emphasis we place in our general thinking on the problem.
We had a little League of Nations meeting in Cambridge last month, to discuss Tinbergen's work.  Tinbergen himself seems very open-minded--and such a delightful man!
I have been doing some arrears of reading, including your more recent contributions in E. J. In reading your December article on ex ante investment & "finance"  which I found most satisfying, I had the pleasure of thinking in my head what you were destined to say in the last paragraph, before I came to it.
I have just finished writing my re-statement of the "dynamic" theory, which is, I think, a great improvement on my book.  I hope you will find it interesting. It has gone off to the typist and ought to be ready to send off in 2 or 3 days. I should like it to appear as soon as you feel you can find room for more by me (in December?)--I havent taken up any space for several years--as I have been throwing out hints in a number of places of the possibility of formulating a simple law of growth and I want to substantiate the claim.  It is largely based on the ideas of the General Theory of Employment;  but I think it gets us a step forward.
2. See letter 772 . Reference is to Tinbergen's Statistical Testing of Business Cycle Theories (1939).
3. J. M. Keynes, "The `Ex-Ante' Theory of the Rate of Interest", Economic Journal XLVII, December 1937, pp. 663-69.
4. Harrod, "Essay in Dynamic Theory" ( 1939:7 ); The Trade Cycle ( 1936:8 ).
5. Harrod, "Scope and Method of Economics" ( 1938:15 ), pp. 403-4. Earlier suggestions that such an equation should be elaborated can be found, for instance, in "Mr. Keynes and Traditional Theory" ( 1937:4 ), p. 86, "Studies in the Theory of Economic Expansion" ( 1937:12 ), p. 496; "Essays in the Theory of Employment" ( 1937:9 ), p. 330.
6. J. M. Keynes, General Theory of Employment (1936).
- a. ALS, four pages on two leaves, in JMK EJ/1/5/221-24. The letter is printed in Keynes, Collected Writings, vol. XIV, p. 301.
b. Written on Christ Church letterhead. Harrod specifies that he is staying at Garrards farm "Till August 11".
c. Ms: «some one».
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