I would wish to "mix"/"contaminate" two threads: 
"Predicting market prices" and "Generators and attractors"
1. I dont want to discuss on Paul's project "externally" as 
done by Jerry and Andrew, that is, invoking information 
problems: "lack of information" or the fact, as Andrew 
says, that the "vertically integrated labor coefficients 
[VILC]" (Tugan's "values") actually depend on prices. All 
this, of course, is true but cannot prevent us to consider 
the problem in theoretical terms.
2. Paul's theoretical project is to predict market prices. 
How could be set this in terms of the theory presented in 
Capital?
First of all, when "market prices" are analized it is 
obvious that in a lot of cases we have "rents". This factor 
should be not explained as a simple "random" factor, 
because involves "structural" conditions of the economy. So 
there is a fraction of the economy in which "market prices" 
are not competitive at all.
Secondly, let us look at the remaining "competitive" 
fraction. In this case the "centre of gravity" (or 
"attractor") CANNOT be "value". A couple of quotations from 
Vol III, Ch. 10:
      The ASSUMPTION that commodities from different
      spheres of production are sold at their values 
      naturally means no more than that this value is 
      the CENTRE OF GRAVITY around which price turns
      and at which its constant rise and fall is balanced
      out. (Penguin, p. 279; capitalization added)
        
After "explaining" the categories of "market value", 
"individual value", etc., Marx says:
      What we have said here of market value holds also 
      for the PRICE OF PRODUCTION, as soon as this TAKES 
      THE PLACE OF MARKET VALUE. The price of production is 
      regulated in each sphere, and regulated too according
      to particular circumstances. But it is again the
      CENTRE AROUND WHICH THE DAILY MARKET PRICES
      REVOLVE, and at which they are balanced out in 
      definite periods. (Penguin, p. 280; 
      capitalization added.)
3. So that, when the "prediction of market prices" is 
attempted IN AN ECONOMY LESS ABSTRACT than that considered 
in Vol. I, what is relevant as "attractor" IS NOT value but 
production price. Certainly, VILC are no longer relevant 
because they are only a particular calculation of prices 
corresponding to a economy with uniform composition of 
capital.
In OPE-L 3764 Paul says:
    One certainly can view production prices as an attractor
    for market prices. Such statistical work as has been 
    done for real economies indicates that both values and 
    production prices are attractors of roughly equal 
    strength. [...]
    
    In practice there is little to chose from on a purely
    statistical basis if one has to chose a predictor of
    market prices. There appears to be little or no 
    statistically significant difference between the 
    predictive power of the two generators. 
    
So that, in terms of purely statistical "strength" there is 
not a clear criterion to choose. According to Paul, in order 
to "predict market prices" one could use production prices 
as "attractors", and need no "Tugan's values".
In terms of Marx's statements in V.III, Ch. 10, there is 
INDEED a criterion to choose. If we are considering the 
"competitive" fraction of the economy, the "attractor" 
must be production price. Marx says clearly that "as soon 
as [production price] TAKES THE PLACE" of value, prices are 
"revolve" around it, not around value (of course, not 
around value as it is calculated in Vol. I).
4. Certainly, Paul invokes his theoretical preference to 
choose VILC as "attractors":
    I prefer to consider values as the principle attractor 
    and production prices as a correction factor. I feel 
    that production price theory rests upon what are, in a 
    sense, derived categories - profits and equal profit 
    rates. These are logically deducible from value 
    relations, whereas the reverse deduction of value
    relations from profit and equal profit rates is much
    harder to do.
However, IMO the "derivation" or "deduction" Paul is 
looking for is invalidated insofar as he uses "Tugan's 
values". This "deduction" is "logically" sound only if we 
can re-establish that all the labor that is distributed 
according to prices was the same objectified in production. 
In this sense is that the law of value regulate prices: 
total labor objectified establishes the LIMIT of that that 
can be appropriated.
Regarding the specific "oscillations" of prices (i.e. 
regarding "market prices"), now they have as "center of 
gravity" production prices, not values. So, the "law of 
value" does not mean that "market prices" "revolve" around 
values. From V.III, Ch. 10 on, "market prices" "revolve" 
around production prices. 
It is important to stress that by means of the VILC it 
is impossible to establish that the total value 
appropriated through prices is the same amount objectified 
in production. This is the reason why Marx's "critics" say, 
precisely, that the "derivation" Paul is looking for is 
"illogical", "erroneous".
Of course, the problem is to use Tugan's definition of 
value, and not consider that, at the stage of Vol III, Part 
2, the "definition" of value is more concrete and thus is 
"modified" to take into account that capitals have a 
different composition.
                                        Alejandro Ramos M.
                                        4.12.96