If software were buildings, how big a fraction of New York city would all the 
software in the world be?  One way to answer this: how much would it cost in 
today's dollars to build New York City; how much would it cost in today's 
dollars to build all the software in the world; take the ratio.  Or: use number 
of man-hours instead of cost in today's dollars.  I need enough detail of how 
the answer is computed to be able to verify its veracity.

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Clarification of Question by philip-ga on 22 May 2002 14:05 PDT

Thank you for the comments.

The purpose of the question is to have a way to visualize the effort
expended on software.  The effort expended to build, say, Manhattan,
is apparent; the effort to construct software is less so.

So one way to answer the question is to take the number of
person-hours to build Manhattan and the number of person-hours to
build all the software in the world and take the ratio.

Another way would be to take the cost (in constant dollars for some
year) to build Manhattan and the cost to build all the software in the
world (for the same year) and take the ratio.

I'd be happy with almost any answer that gave reasonable estimates and
was based on  stated, plausible assumptions.  I'd prefer the region
covered is Manhattan, but if it's easier to compute for, say, all five
burroughs, that's fine, as long as the assumption is stated. 
Similarly, I'd prefer the cost of all software written for any purpose
anywhere, but if its easiest to compute for all software written in
the US or all software sold commercially, that's fine too, as long as
the assumption is stated.

I would like a measure that corresponds to effort, rather than return.
 Hence, total value paid to programmers is fine; total value reaped by
selling the software is less useful.  Total value paid to builders is
fine; total value of the buildings including real-estate appreciation
is less useful.

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Clarification of Question by philip-ga on 22 May 2002 14:08 PDT

A typo: where it says "cost to build all the software in the
world (for the same year)" the parenthesised part should read
"(in constant dollars for the same year)".

I suppose if you want a detailed answer, you would need to provide more details 
in the question.  What do you mean by "build New York City"?  How do you want 
to quantify the cost of the city?  Are you including only the bricks and 
morter?  Do you also want to factor in the cost of labor?  The property?  
Presumably if the city weren't already built, the land would be less 
expensive.  So how do you want to value the land?  What about the businesses?  
Do you want to build a city that's ready to be moved into?  Or take it all the 
way to the inclusion of theaters, restaurants, etc.  Do you really mean New 
York City, or do you just mean Manhattan?  New York City includes the boroughs 
of Queens, Staten Island, the Bronx, and Brooklyn.  In fact, Brooklyn is such a 
large borough that if it weren't part of NYC it would be one of the five 
largest cities in the country.  So do you want to factor it in or leave it out?

And what do you mean by "all the software in the world"?  Every program that's 
ever been written?  Written and sold commercially?  It takes money to write the 
programs that never make it to the store shelves, too.  Do you want to include 
every copy of every program?  Or just the cost of developing it?  Or just the 
amount of money spent on purchasing it?  Are you including games?  Just 
software written for home use?  Are you including proprietary software 
commissioned by companies for their in-house business use only?  What about 
pirated software?  Do you want to consider that as lost revenue?  How do you 
measure that? 

Hmm... things to think about.

I won't do the research on it, but to clarify the variables: 

The easiest way to find out the 'cost' of New York City is just take
the market value of every single public and private property in the
city. Since not all properties are for sale, the alternate is to take
the appraised values, for property tax purposes, or the insured
values.

Software is a bit harder. It would either be the sum of all software
programmers' salaries to this date, or alternately the total sales to
date of all software titles ever released.