NEW YORK (CNN/Money) - In what could be a troubling sign for retailers hoping for a strong holiday shopping season, consumer confidence took one of its biggest plunges ever this week, according to a new poll.

The ABC News/Money magazine Consumer Comfort Index dropped five points to -9 on its scale of +100 to -100. It's fallen that far in a single week only 23 times in 988 weeks.

The poll follows reports oflackluster sales on "Black Friday", traditionally the busiest shopping day of the year and a time when retailers move from operating at a loss, "in the red," to turning a profit, "in the black".

The ABC/Money index is based on Americans' ratings of the current economy, buying climate and personal finances. Its -9 today is down from -4 last week and -5 a month ago, and similar to its level after last Thanksgiving, -11. The poll's long-time average is also -9.

Confidence is stronger among better-off Americans. The index is +41 among higher-income people while -38 among those with the lowest incomes; +3 among college graduates while -31 among high-school dropouts; -5 among whites but -24 among blacks; and +2 among men but -19 among women.

The index is far higher among Republicans (+23), than independents (-14) or Democrats (-36), as has been the case all year. But as noted, that's less of a gap than at its peak, +43 among Republicans and -47 among Democrats in July.

Taken as a whole, forty percent of Americans rate the economy as excellent or good; it was 43 percent last week. The highest was 80 percent on Jan. 16, 2000. The lowest was seven percent in late 1991 and early 1992.

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Fifty-eight percent say their own finances are excellent or good; it was 60 percent last week. The best was 70 percent on Aug. 30, 1998, matched in January 2000. The worst was 42 percent on March 14, 1993.

Thirty-nine percent say it's an excellent or good time to buy things; unchanged from last week. The best was 57 percent on Jan. 16, 2000. The worst was 20 percent in fall 1990.

The ABC News/Money magazine Consumer Comfort Index represents a rolling average based on telephone interviews with a random sample of about 1,000 adults nationwide each month. This week's results are based on 1,000 interviews in the four weeks ending Nov. 28, 2004, and have an error margin of plus or minus three percentage points.