Westport's newly certified 2010 Grand List of all taxable property, reflecting sharp declines in the value of local residential and commercial properties, dropped 12.4 percent from 2009.

The figures, released Thursday afternoon by town officials, show the net 2010 Grand List stands at $9,553,989,667, a decrease from the net 2009 Grand List of $10,910,243,025.

"This was due mainly to a 13 percent decrease in residential real estate and a 15 percent decrease in commercial real estate since the last revaluation in 2005," Assessor Paul Friia said in a statement. Friia on Thursday signed the Grand List -- reflecting the value of all taxable properties in town as of last Oct. 1 -- as required by state statute.

The list reflects the total assessed value of real estate, motor vehicles and personal property in Westport.

Motor vehicles and personal property are valued annually, he said, while real estate is updated every five years.

The latest real estate assessments are based on market values determined by last year's townwide revaluation.

Here's a breakdown comparing the major Grand List categories between the 2010 and 2009 Grand Lists:

REAL ESTATE:

2010 -- $9,002,766,290

2009 -- $10,377,628,396

A decrease of $1,374,862,106, or 13.2 percent

PERSONAL PROPERTY

2010 -- $253,482,382

2009 -- $248,590,859

An increase of $4,891,523, or 1.9 percent

MOTOR VEHICLES

2010 -- $297,740,995

2009 -- $284,023,770

A rise of $13,717,225, or 4.8 percent

Following is the list of Westport's top 10 taxpayers and the assessed value of their holdings:

Connecticut Light & Power, Inc. Personal Property $115,676,470

Nyala Farms, Inc. 60 Nyala Farms Road 78,274,120

Marc & Cathy Lasry Residential 22,607,600

Riverside Office 285 & 355, LLC 285 & 355 Riverside Ave. 21,990,600

Heyman, Ronnie F. & Samuel J., Est. Residential 19,994,700

Roseville Estates Inc. 1777 Post Road East 19,832,960

Allianz Life Insurance Co. 55 Greens Farms Road 19,075,500

Byelas Irving Irrevocable Trust 1790 Post Road East 17,112,200

Bridgewater Associates Inc. 1 Glendinning Place 15,818,830

Westjust LLC 1850 Post Road East 14,519,200