EXHIBIT A
JOINT FILING AGREEMENT
In accordance with Rule 13d-1(k)(l) under the Securities Exchange Act of 1934,
as amended, the undersigned hereby agree to the joint filing of the attached
Schedule 13G, and any and all amendments thereto, and expressly authorize
AMVESCAP PLC, as the ultimate parent company of each of its undersigned
subsidiaries, to file such Schedule 13G, and any and all amendments thereto, on
behalf of each of them.
Dated: January 23, 2007 AMVESCAP PLC
By: /s/ ▇▇▇▇ ▇▇▇▇▇▇▇▇
------------------------------------
Name: ▇▇▇▇ ▇▇▇▇▇▇▇▇
Title: Global Compliance Director
AIM Advisors, Inc.
By: /s/ ▇▇▇▇ ▇▇▇▇▇▇▇▇
------------------------------------
Name: ▇▇▇▇ ▇▇▇▇▇▇▇▇
Title: Chief Compliance Officer
AIM Funds Management Inc.
By: /s/ ▇▇▇▇▇ ▇▇▇▇▇▇
------------------------------------
Name: ▇▇▇▇▇ ▇▇▇▇▇▇
Title: Chief Compliance Officer
INVESCO Management S.A.
By: /s/ ▇▇▇▇▇ ▇▇▇▇▇▇▇▇
------------------------------------
Name: ▇▇▇▇▇ ▇▇▇▇▇▇▇▇
Title: Head of Investment Operations
PowerShares Capital Management LLC
By: /s/ ▇▇▇▇▇ ▇▇▇▇▇▇▇▇▇
------------------------------------
Name: ▇▇▇▇▇ ▇▇▇▇▇▇▇▇▇
Title: General Counsel & COO
