what are the nation's 10 largest residential real estate companies by
sales volume and what is the source of this info?

Hello chris1949-ga,

Thank you for your question. 


The top real estate companies ranked by sales volume in millions are
the following:
(residential)

1 NRT Inc. $117,119.0 
2 Weichert, Realtors  19,500.00 
3 Long & Foster Real Estate Inc. 18,496.52 
4 HomeServices of America Inc. 18,379.79 
5 Prudential California Realty/Americana Realty 
Purchased by HomeServices.com, March 2002 13,385.32 
6 GMAC HomeServices Inc. dba GMAC RealEstate 11,245.99 
7 Arvida Realty Services 
Purchased by NRT, April 2002 8,595.00 
8 The DeWolfe Companies Inc.  6,629.77 
9 Prudential Fox & Roach, Realtors 6,492.15 
10 Alain Pinel Inc., Realtors 5,300.00 

Source: Realtor Magazine Online
http://www.realtor.org/rmomag.nsf/pages/coverfeaturejuly02a?opendocument#three


Additional information that may interest you:

TOP 100 COMPANIES: Ranked by Transaction Sides
http://www.realtor.org/rmomag.nsf/pages/coverfeaturejuly02a?opendocument#three

Top 100 Ranked By Sales Volume
http://www.narauctionsource.com/rmomag.nsf/pages/top100salesvolume

Search Criteria:
Top residencial real estate companies by sales


I hope you find this helpful and if there is anything that I've
written that needs clarification, please ask before you rate this
answer.

Best Regards,
Bobbie7-ga