
Estimate: Top US Firms Have Over 700,000 Job Openings - gne1963
http://mast-economy.blogspot.com/2009/01/estimate-top-us-firms-have-over-700000.html
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nostrademons
The "100 companies is a representative sample" is a big assumption. The linked
article says those 100 companies were all Fortune 500: that implies that
there's a very large likelihood that they are bigger than the other companies
in the Fortune 1000. Bigger companies naturally have more job openings.

Even if this is true, it doesn't necessarily mean the economy's doing better.
It's pretty likely that the job openings require skills that the newly
unemployed workers do not have. Otherwise, they'd be filled. You can't hire a
former real estate agent at Google and expect him to be immediately
productive. (Hell, you usually can't hire a software engineer at Google and
expect him to be immediately productive, but at least you can hire him.)

The issue with recessions is misallocation of capital, and it can't be fixed
with a magic wand. You generally have to wait for people to retrain in new,
productive areas of the economy, and for capital to be liquidated and
entrepreneurs to find new uses for it. That's why it takes ~4 years instead of
~4 months.

~~~
gne1963
The samples were taken from a random selection of 100 of the top 1000 firms.
The real question is how to make that selection of 100 firms so that
statistically the sample size is a representative sampling. The goal is not to
determine whether or not the jobs are available to those folks who may have
just been laid off. The goal is to determine just how many job opening do
exist in the Fortune 1000 without needing to hit every single job board of
every one of those 1000 companies... surely there is a statistician who can
solve that one? ;-)

~~~
nostrademons
From the link on your page:

"Yesterday we embarked on a research project to find current job openings. We
started with 21 firms (with 18,839 open positions) and now we're up to data
from 100 of them. (All Fortune 500)"

The chance that a random sample of 100 firms are _all_ in the top half of the
sample universe is 2^100 = about a decillion. Doesn't really look random to
me.

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gne1963
Thanks, nice catch and that post needs to be changed... momentarily... The
universe was truely from the Fortune 1000 from the list publish online... not
the top 500 only...

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gne1963
You can see my confusion is somewhat born out by hitting this link... it is
labeled 500 when actually it lists the top 1000...

[http://money.cnn.com/magazines/fortune/fortune500/2008/full_...](http://money.cnn.com/magazines/fortune/fortune500/2008/full_list/)

~~~
gne1963
So here is the methodology: 1\. Hit the site above. 2\. Randomly pick a
company from the list... for instance: 3\. Pick Paychex Systems... company 921
on Fortunes list... 4\. On their site they list 137 job openings... 5\. Add
that to the total... 6\. Repeat until you have a representative sample size

Question: Using an appropriate random number generation between 1 and 1000,
what is the sample size required to then estimate the total job openings on
the 1000 sites?

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anamax
Job opening on a company's "career site" are a very poor predictor of the
number of people that company would hire if could find suitable candidates.

In some cases, the listing is to satisfy an HR rule and the person to be hired
has already been selected. In other cases, it's "maybe someone wonderful will
wander in".

And then there are the hires that happen without a listing.

I'd guess that the actual uncertainty in the total is more a function of the
uncertainty in the numbers than it is in the sampling.

~~~
gne1963
>I'd guess that the actual uncertainty >in the total is more a function of the
>uncertainty in the numbers than it is in >the sampling.

totally agree. As with any indicator there is quite a bit of uncertainty. And
as you suggest "there are the hires that happen without a listing..." Most
career counselors would agree that there are actually more hidden jobs than
what the boards suggest...

So... your argument might just boost the number if we add some multiplier into
the model based on the jobs actually posted.

thanks! gne1963

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gne1963
So here is the methodology: 1\. Hit
[http://money.cnn.com/magazines/fortune/fortune500/2008/full_...](http://money.cnn.com/magazines/fortune/fortune500/2008/full_list/)
2\. Randomly pick a company from the list... for instance: Pick Paychex
Systems... company 921 on Fortunes list...On their career site they list 137
current job openings... 3\. Add that to your total... 4\. Repeat until you
have a representative sample. 5\. Extrapolate to 1000...

Question: Using an appropriate random number generation between 1 and 1000,
what is the sample size required to then estimate the total job openings on
the 1000 sites?

~~~
NyxWulf
Well here are a couple of things: you show 99 records on your excel
spreadsheet, with an average of 709 and a standard deviation of 1073.

With that large of a standard deviation and that average you can't assume a
normal distribution so you need to use the T distribution.

Using the T distribution at a 95% confidence level I come up with an estimated
average of [495, 923] which results in a number of jobs in the top 1000 from
495,000 to 923,000 with a 95% certainty.

Just for kicks I wanted to see what would happen if you sampled 500 times but
had that same standard deviation. At that point your spread would be about +/-
100 for the average value of X.

If you are looking for a singular number you'll need to check all 1,000 of
them, otherwise it will be an estimated range.

~~~
gne1963
Thanks!

So what if I did another 100 random sample resulting a "better" (lower) std
dev? At what level of std dev could one assume a normal distribution out to
1000?

gne

