It is hard to say how much more nervous consumers are today than they were before the stock market and the financial system started their wild ride last month. But as shopping center owners and retailers gear up for the most challenging holiday season in memory, the outlook is a decidedly mixed bag, according a national survey of 21,000 households published last Thursday by The Nielsen Co. Overall, unit sales are expected to decline about eight-tenths of a percent during the period between Thanksgiving and New Year’s Day. Sales could increase 4.7 percent, to $98 billion, but increased commodity sales account for that bump. A few categories of retailers will make out better than others. Big-box discounters, grocery stores and mass merchandisers may have the best shot at holding the line, as about 50 percent of those surveyed said they would spend about the same in those stores this year as they did last year. Almost as many consumers—46 percent—said they expected to spend the same in department stores as they did last year. But the bad news is that 28 percent of consumers say that they plan to spend less in department stores. Electronics stores may also be headed for a softer sales season, as an identical 28 percent of consumers said they plan to cut back. By comparison, 20 percent expect to spend less in toy stores, and mass-merchandising outlets, bookstores, and hardware and home improvement stores all received expectations of less spending from 19 percent of respondents. Not surprisingly, higher-income consumers appear to feel that they are in a better position than members of other income categories to repeat last year’s holiday outlays. Fifty-seven percent of households in the $100,000-plus range intend to spend about the same as they did in 2007. By comparison, only 47 percent of households in the $20,000-to-$30,000 group plan to spend the same. But most merchants will probably not be able to rely solely on upper-income customers to save the season. The Nielsen study shows that 32 percent of households earning $100,000 and up plan to cut back on holiday spending. Indeed, one striking result was that a wide range of income groups are inclined to spend less. Across all income categories, 35 percent of consumers plan to cut back on their expenditures, and only 6 percent expect to spend more than they did last year. For example, 32 percent of the highest-income category are looking at thriftier holidays. That is only slightly less than the 36 percent of the $20,000-to-$30,000 category who expect to spend less this year.