WHEN times get tough, people with an abundance of disposable income are inclined to keep disposing of it while the rest of us are forced to keep our thinner wallets in our pockets.

With that in mind, Tobias Levkovich, Citigroup’s chief United States equity strategist, has created the Living Large Index, comprising stocks of businesses that cater to affluent consumers. Profits and share prices of luxury-goods makers, higher-end retailers and travel and entertainment companies should hold up even if businesses serving them suffer from difficult economic conditions, he said.

His index includes names like American Express, Tiffany, Saks, Nordstrom, Royal Caribbean Cruises, the casino operator Wynn Resorts and Callaway Golf.

Mr. Levkovich could have chosen companies with a more exclusive clientele but decided to focus less on the superrich than on modestly well-off people. There are far more members of the second group than the first, making the companies that cater to them a greater piece of the economic and investment pie. “These are upper-income people, but not people who are buying business jets or Picassos,” he said.