The Alliance for Downtown New York has issued a report that found that in 2007 21 new residential buildings were opened in Manhattan south of Chambers Street with 3,300 units, a 15 percent increase to the area's inventory.

Upon full occupancy of these units, Lower Manhattan will be come to more than 50,000 residents in more than 25,100 units in 295 residential buildings, the report maintained.

The report indicated that 35 more residential projects are planned or under construction in Lower Manhattan that will add at least 5,000 more units to the inventory and 25 of those projects with 4,500 units will come on line this year and bring the area's resident population to almost 59,000.

The average household income of Lower Manhattan residents rose from $152,800 in 2004 to $241,967 last year, according to the report. The median income increased from $111,000 in 2004 to $162,700 in 2007, it continued, adding that "this is nearly three times greater than the median Manhattan household income."

Couples without children, the report said, now account for 42 percent of the households in Lower Manhattan while 7 percent have roommates, 26 percent are one-person households, 2 percent are single parents and 23 percent are couples with children.

The majority of projects planned or under construction in Lower Manhattan are condos, while 20 percent are rentals, but the Alliance noted that about 19 percent of the new developments have not been announced publicly and "brokers report that developers are waiting to see which will be more viable in the changing real estate market."

The study found that 67 percent of the units added between 2000 and 2007 were conversions.

More than 1,200 units were sold last year in Lower Manhattan, a record, and sales prices climbed steadily reaching $1,052 a square foot in December, the report found, a 15 percent increase over the previous year.