NEW YORK, Dec 21 (Reuters) - - Cotton futures ended firmer Tuesday on buying by small investors in thin business with investors apparently gone until after the New Year holidays, analysts said.

The market was shut Monday for Christmas.

The key March cotton futures added 0.67 cent to close at 87.91 cents per lb, dealing from 87.24 to 88.12 cents.

Volume traded Tuesday hit nearly 3,100 lots, almost 85 percent under the 30-day norm, Thomson Reuters preliminary data showed.

Since scaling a record top over $2.20 a lb in early March, cotton demand has shrunk and prices have more than halved. If it stays at its present level, cotton is on track to be the worst performing commodity market for 2011, a year after rising over 90 percent in 2010 as the second best performing market.

'It's a total holiday atmosphere,' said Mike Stevens, an independent expert in Mandeville, Louisiana.

He said the market's subdued level of activity will likely last until the end of 2011 this week, with many funds having already closed their books and not coming back until next month.

Fundamentally, traders believe cotton will not be an investor darling going into 2012.

They point to weak demand caused by fears the debt and budget crisis in the EU and the United States would continue to adversely affect cotton demand.

Total volume traded last Friday reached 2,975 lots, its lowest level since late in 2008, ICE Futures U.S. data showed.

Open interest, an indicator of investor exposure, was at 151,176 lots last Friday, exchange data showed.