Wal-Mart data compared to 1997 U.S. Census economic data

I spent a fair amount of time going through the U.S. Census material to try to figure out what the percentage is that Wal-Mart has of the overall retailing space that it operates in here in the U.S.

Let me quickly breakout the 4 NAICS codes that apply when comparing Wal-Mart data to U.S. Census economic data.
They are:

NAICS
code      Description
445110   Supermarkets & other grocery
445120   Convenience stores
452110   Department stores
452910   Warehouse clubs and superstores

Total retail sales in the United States in 1997 for the four categories listed above were:
$670.277 billion

Wal-Mart's 1997 (calendar) U.S. sales were:
$104.488 billion

Wal-Mart's 1997 sales represented 15.59% of the total U.S. sales in the main general categories it competes in.

[I made the selection of those specific NAICS categories above based on the 1997 Economic Census Retail Trade publication by the U.S. Census Bureau published in October 2000. The reference number for this publication is EC97R44S-SB. It may seem odd that I included "Convenience Stores" as Wal-Mart would not seem to compete in this category. I did so because there are only two categories of "Grocery Stores" in the entire census. These are "Supermarkets & other grocery (except convenience) stores" and "Convenience stores." The U.S. Census Bureau generally includes Convenience Stores when they are discussing the overall grocery business. Wal-Mart is in the grocery business. For a more advanced look at all of the NAICS retail categories, see the first comment below.]