SEMAINE D'ÉTUDE SUR LE ROLE DE L'ANALYSE ECONOMETRIQUE ETC.

421

similar to a diagonal matrix, so that there exists a non-singular
matrix P such that (®):

(5.21)

DB =PHP

where H is diagonal and has for diagonal elements the latent
roots of DB. Let:

(5.22)

(5-23)

(5.24)

Then every such term can bè Writctai €

(5.25) (DB) DVI(o:-PH



DO.

30

We know that every diagonal element of the diagonal
matrix A is less than unity in absolute value (indeed, we are
assuming that some of the diagonal elements are zero). More
over, if we are prepared to maintain the stability assumption
on DB which was slipped in some time ago, every diagonal
element of the diagonal matrix H will also be less than unity
in absolute value. It follows that every element of every term
in the expansion of W(1) other than the first is composed of
a sum of terms each of which involves at least the product of

(*) The assumption involved is, of course. very weak and is made for
pase of exposition

6 |

Fisher - pag. 37