~T 
3C"-SSION 
WoLD 
Prof. FISHER has given us an excellent survey of structura 
properties and estimation techniques for the dynamic econometric 
models known as interdependent (ID) systems and causal chain 
(CC) systems. Having over many years emphasized the clearcut 
rationale of CC systems, also known as recursive systems, I appre 
ciate verv much the fair treatment he has given this approach. His 
review of the ID approach is a very clarifying exposition of the many 
estimation techniques that have been proposed for ID-systems, a 
multitude of techniques that are known to work and give reconci- 
lable results when applied to small systems, whereas the situation is 
far from clear when it comes to large systems with many unknown 
parameters. The very pluralism of the methods is an indication that 
the problem of parameter estimation in large ID-systems has not 
yet found a satisfactory solution. 
The questions at issue are technical matter, Hence the first thing 
is to summarize what the two types models have and have not in 
common, so as to be able to locate and if possible clear up any 
divergencies that may exist. Three points will be mentioned. 
(1) In the beginning of section 2, Prof. FISHER states three as: 
sumptions R 1-3 that are to be satisfied by a CC system, al. in 
accordance with current theory of the probability structure and 
61] Fisher - pag. 6=