Sunday, November 30, 2014

G7: Trying to get the damn door open

Soon as we got past that first model I hit a brick wall. There are five models to consider in Part 2 of Chapter 1 of Part 1 of The Craft of Economic Modeling. But it's like they left something out.

The first model we did, that one's not even numbered I guess. In Part 2 of the chapter they talk about five models, starting with number one:

Model 1 just sets out the variables and identities that are central to the system of national accounts used in the United States. We may call it a pure-accounting model because it makes connections among variables based only on accounting definitions, not on economic behavior.


On page 9 he gets into Model 1. There is a pretty interesting review of how the NIPA categories break down. Clopper Almon explains it well. For example:

Business current transfer payments (net) include legal settlements and theft losses. We first subtract the entire amount and then add back in the portion which went to persons. The stolen case of Bourbon is counted as income to the thief and, by the way, appears in Personal consumption expenditure and thus in GDP.

And I really like how he every once in a while tells you what he thinks:

If we may, for the moment, skip the Statistical discrepancy, which should be zero conceptually, we have reached Personal income before government action. This item is not in the official accounts, but I find it a convenient point of reference.

But things are missing. He writes
We can now summarize this first model in the following master file which shows the actual commands to the software we use to compute this model.

And he provides the text for that "master" file. But... is "master" the name of the file or just a generic term? And if it is the name, then what is the file extension?

I think maybe the file is called master.add and I'm going with that for now. But I'm not sure. And where is the data? He did say in passing that

The variable names shown in the code column are the ones used in the Quarterly Income and Product (Quip) data bank...

But I had to dig to find that quote, and now I have to dig to find a "Quip" file, and then I have to hope I've been making good guesses.

Things are missing. Yeah, yeah, I remember: In the intro Almon wrote, "Of course, as in any craft, a book can only help, not replace, a living teacher."

Yeah, yeah.

// UPDATE 4:45 pm

The Master file doesn't have an extension. And the first QUIP.ZIP file I found was an old one, from 2002, from the Inforum EconData Archives. You don't want to use that one. Too many variable names have changed. I started fixing errors, with some success, but it just got to be too much.

I found a better QUIP file. I hope, better. I didn't even test it out yet. Between fixing errors in the first QUIP and looking for a newer one, I didn't have any energy left to look at it once I found it.

Actually, what did I find? It was the AMI file, the "Accelerator-Multiplier Interaction" model, a ZIP file with a few versions of the MASTER file (no extension) and a G.CFG and the QUIP bank files and some other stuff.

This is starting to come together. A lot of work, but I'm making progress. Pretty soon I'll be able to get thru that first chapter. I'm itching to do more.


Jerry said...

Couple of (probably useless) comments:

There is an AMI with (I think) all of the same stuff that the AMI you found has (master, etc), at: c:/(pdg|g7|whatever)/WinRoot/Models/AMI/

I noticed that there is some stuff like this in Run.cpp:
#include "c:\pdg\rproto.h"
#include "c:\pdg\"
#include "c:\pdg\"
so, that may be an issue when you get to compiling a new model, if you have that stuff in c:\g7\ instead. But, maybe not, I don't yet understand that part. (I guess you can just edit it and change them to "g7"s, but, there might be more stuff like that around somewhere.)

There are some batch files lying around in the AMI/ which might provide clues about what the other guys were doing, e.g.:

C:\PDG\WinRoot\Models\AMI>type GO.BAT
copy bws.* rws.*
run 1995.1 2000.4 rhoadj.fix
copy rws.* histsim.*

C:\PDG\WinRoot\Models\AMI>type model.bat
path c:\pdg;c:\Borland\bcc55\bin;%PATH%;
del run.obj
del hearta.obj
del run.tds
del run.exe
build master
make -frun.bpr

Jerry said...

There are also some instructions on page 18, looks like.

The Arthurian said...

Okay. So I went back and looked in the original TEMP folder where I unzipped my original download of PDG.EXE.

There is a PDG folder in TEMP, and sure enough, there is a WinRoot folder in that PDG folder. And a Models folder in that. And an AMI folder in that. Oh, ouch!

Thanks Jerry.