Cost of Savings Index (COSI) is the weighted average of all the interest rates paid on Certificate of Deposits held by individual depositors of Wells Fargo as of the last business day of each month. COSI is also known as the Wells Fargo Cost of Savings Index or Wells COSI.
COSI is calculated each month on the last business day of the month and is published on Wells Fargo website on the business day preceding the fifteenth day of the following month. For example, the COSI for Nov 2013 was published on Fri, Dec 13, 2013.
COSI is used as an index in a number of Adjustable Rate Mortgages (ARMs). It is viewed as a stable index and lags the other interest rate indexes. This is because COSI is based on interest rates on deposit accounts which tend to be less volatile than the general interest rate movements.
COSI was originally published by World Savings and it represented the weighted average interest rate on federally insured deposit accounts held by depositors at World Savings Bank, FSB.
World Savings Bank, FSB was a federally insured depository institution and a subsidiary of Golden West Financial Corporation (GWFC). World Savings Bank was established on Oct 8, 1987 under the name Watchung Hills Bank for Savings. The bank changed its name to World Savings Bank, F.S.B on Jan 21, 1995. The FDIC Number for World savings Bank was 27076. GWFC was listed in New York Exchange under the Ticker Symbol GDW. GDW was delisted from NYSE on Oct 2, 2006.
In October 2006, Wachovia Corporation acquired Golden West Financial Corporation, including World Savings. The World Savings COSI was discontinued in June 2007 and replaced by the Wachovia COSI. On Dec 31, 2007 World Savings Bank, FSB was renamed to Wachovia Mortgage, FSB.
On Nov 1, 2009 Wachovia Mortgage, FSB was renamed as Wells Fargo Bank Southwest, NA. On the same day, the Bank merged into and has since operated as part of Wells Fargo Bank, National Association. In the present form COSI is now a measure of the interest rate paid on certificate of deposits held by individuals at Wells Fargo.
COSI rates up to July 2007 are the World Savings COSI. From July 2007 to October 2009, COSI values reflect Wachovia COSI. From November 2009, values reflect Wells COSI.
Updated: Oct 12, 2018