What is the total dollar value of all credit card transactions in the
US (or world wide, either is fine)?

This is not the aggregate credit card company percentage, but instead
is the gross value of all purchases made with any type of credit card
(e.g. Mastercard, Visa, Amex, Discover,...)

The data needs to be authoritative and citable for academic publication.

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Clarification of Question by seekthetruth-ga on 17 Jun 2005 12:24 PDT

Data should be for any given year in the past five years.  Finer grain
data, such as quarterly, that can easily be aggregated is also fine.

Hi seekthetruth:

Thanks for the interesting question. The most authoritative source on
electronic payments (which include credit card payments) in the U.S.
can be found at the Federal Reserve.

Federal Reserve Financial Services
URL: http://www.frbservices.org

It appears that the most recent complete study done is the "2004
Federal Reserve Payments Study", which examines the years 2000 - 2003:

2004 Electronic Payments Study
URL: http://www.frbservices.org/Retail/pdf/2004EPStudy.pdf
Quote: (from page 5)
********************
Values for the Years 2000 and 2003 (Millions)

Payment Instrument                2000           2003        CAGR
General Purpose Credit Cards   $1,072,555    $1,409,744       9.5%
Private Label Credit Cards       $204,771      $283,758      11.5%
********************
(CAGR) = Compounded Annual Growth Rate

This puts the total credit cards payments in the U.S. for 2003 at
approximately 1.7 trillion dollars.

Given that the overall credit cards transaction value is rising at
about 10% a year, that would put the estimated total value for 2004 at
1.9 trillion and for 2005 at 2.1 trillion.

I cannot think of any more authoritative source than this. 

Search Strategy (on Google):
* "gross value" transactions "credit cards" trillion

I hope this helps. 

websearcher

This was a complete and very helpful answer.  It met my needs exactly.
 Thanks to the researcher.