STOCK-BASED COMPENSATION

3 Months Ended

Mar. 31, 2012

STOCK-BASED COMPENSATION [Abstract]

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION

Stock-based compensation granted includes stock options, performance stock awards, restricted stock awards and deferred directors' compensation.  Stock-based compensation expense was as follows:

	Three Months Ended March 31,
	2012		2011
	($ in millions)
Stock-based compensation	$	1.9	$	2.0
Mark-to-market adjustments		0.9		1.0
Total expense	$	2.8	$	3.0

The fair value of each stock option granted, which typically vests ratably over three years, but not less than one year, was estimated on the date of grant, using the Black-Scholes option-pricing model with the following weighted-average assumptions:

Grant date	2012			2011
Dividend yield		3.65	%		4.32	%
Risk-free interest rate		1.36	%		3.05	%
Expected volatility		43	%		42	%
Expected life (years)		7.0			7.0
Grant fair value (per option)	$	6.55		$	5.48
Exercise price	$	21.92		$	18.78
Shares granted		480,250			575,000

Dividend yield for 2012 and 2011 was based on a historical average.  Risk-free interest rate was based on zero coupon U.S. Treasury securities rates for the expected life of the options.  Expected volatility was based on our historical stock price movements, as we believe that historical experience is the best available indicator of the expected volatility.  Expected life of the option grant was based on historical exercise and cancellation patterns, as we believe that historical experience is the best estimate of future exercise patterns.