16. Stock Plans

Defined Contribution Plans—Substantially all permanent employees are eligible to participate in defined contribution plans provided by the Company. Under these plans, participants may make contributions into a variety of funds, including a fund that is fully invested in Company stock. Employees are not required to allocate any funds to Company stock, which allows employees to limit their exposure to market changes in the Company's stock price. Employees may generally reallocate their account balances on a daily basis. The only limit on the frequency of reallocations applies to changes involving Company stock investments by employees classified as insiders or restricted personnel under the Company's insider trading policy.

Stock compensation expense relating to employer contributions under defined contribution plans for fiscal years ended September 30, 2013, 2012 and 2011 was $14.6 million, $15.9 million and $17.2 million, respectively. Issuances and repurchases of AECOM common stock related to employee participants' contributions to and withdrawals from these defined contribution plans are included as issuances and repurchases of stock in the accompanying Consolidated Statements of Stockholders' Equity and of Cash Flows.

Stock Incentive Plans—Under the 2006 Stock Incentive Plan, the Company has up to 17.6 million securities remaining available for future issuance under stock options or restricted stock awards as of September 30, 2013. Stock options may be granted to employees and non-employee directors with an exercise price not less than the fair market value of the stock on the date of grant. Unexercised options expire seven years after date of grant. During the years ended September 30, 2013, 2012 and 2011, compensation expense recognized relating to employee stock options as a result of the fair value method was $0.3 million, $2.4 million and $4.6 million, respectively. Unrecognized compensation expense relating to employee stock options outstanding as of September 30, 2013 was $0.2 million to be recognized on a straight-line basis over the awards' respective vesting periods which are generally three years.

The Company did not grant any employee stock options during the twelve months ended September 30, 2013 and 2012. The fair value of the Company's stock options granted to employees were determined using the following weighted average assumptions:



Dividend yield	0.0	%
Expected volatility	38.6	%
Risk-free interest rate	1.5	%
Term (in years)	4.5

The weighted average grant-date fair value of stock options granted during the year ended September 30, 2011 was $9.43.

During the three years in the period ended September 30, 2013, option activity was as follows:

	Number of Options			Weighted Average Exercise Price

	(in millions)
Balance, September 30, 2010		3.1		$	19.09
Granted		0.4			27.65
Exercised		(0.5	)		12.28
Cancelled		(0.1	)		23.91

Balance, September 30, 2011		2.9			21.38
Granted		—			—
Exercised		(0.4	)		11.40
Cancelled		—			26.23

Balance, September 30, 2012		2.5			22.81
Granted		—			—
Exercised		(0.8	)		18.31
Cancelled		(0.1	)		26.83

Balance, September 30, 2013		1.6		$	24.73

Exercisable as of September 30, 2011		2.1		$	19.55

Exercisable as of September 30, 2012		2.1		$	22.07

Exercisable as of September 30, 2013		1.4		$	24.51

The following table summarizes information concerning outstanding and exercisable options as of September 30, 2013:

	Options Outstanding								Options Exercisable

	Number Outstanding as of September 30, 2013		Weighted Average Remaining Contractual Life		Weighted Average Exercise Price		Aggregate Intrinsic Value		Number Exercisable as of September 30, 2013		Weighted Average Remaining Contractual Life		Weighted Average Exercise Price
	(in millions)						(in millions)		(in millions)
Range of Exercise Prices
$14.20 - $23.94		0.6		1.90	$	22.20	$	5.8		0.6		1.90	$	22.20
24.45 - 26.47		0.4		2.96		24.56		2.4		0.4		2.96		24.56
27.00 - 34.00		0.6		2.99		27.84		1.9		0.4		2.68		27.91

14.20 - 34.00		1.6		2.53		24.73	$	10.1		1.4		2.40		24.51

The remaining contractual life of options outstanding at September 30, 2013, range from 0.10 to 4.51 years and have a weighted average remaining contractual life of 2.53 years. The aggregate intrinsic value of stock options exercised during the years ended September 30, 2013, 2012 and 2011 was $7.9 million, $3.9 million and $7.8 million, respectively.

The Company grants stock units to employees under the Performance Earnings Program (PEP), whereby units are earned and issued dependent upon meeting established performance objectives and vesting over a three-year period. Additionally, the Company issues restricted stock units, which are earned based on service conditions. Total compensation expense related to these share based payments was $31.1 million, $24.1 million and $20.4 million during the years ended September 30, 2013, 2012 and 2011, respectively. Unrecognized compensation expense related to PEP units and restricted stock units outstanding as of September 30, 2013 was $52.4 million, to be recognized on a straight-line basis over the awards' respective vesting periods which are generally three years.

Cash flow attributable to tax benefits resulting from tax deductions in excess of compensation cost recognized for those stock options (excess tax benefits) is classified as financing cash flows. Excess tax benefits of $1.8 million, $1.3 million and $61.2 million for the years ended September 30, 2013, 2012 and 2011, respectively, have been classified as financing cash inflows in the Consolidated Statements of Cash Flows.