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: February 14, 2007 AMVESCAP PLC By: /s/ Xxxx Xxxxxxxx ------------------------------------ Name: Xxxx Xxxxxxxx Title: SVP/Global Compliance Director AIM Advisors, Inc. By: /s/ Xxxx X. Xxxxxxxx ------------------------------------ Name: Xxxx X. Xxxxxxxx Title: Chief Compliance Officer AIM Capital Management, Inc. By: /s/ Xxxx X. Xxxxxxxx ------------------------------------ Name: Xxxx X. Xxxxxxxx Title: Chief Compliance Officer AIM Funds Management, Inc. By: /s/ Xxxxx Xxxxxx ------------------------------------ Name: Xxxxx Xxxxxx Title: Vice President, Compliance & Chief Compliance Officer AIM Private Asset Management, Inc. By: /s/ Xxxx X. Xxxxxxxx ------------------------------------ Name: Xxxx X. Xxxxxxxx Title: Chief Compliance Officer AMVESCAP National Trust Company By: /s/ Xxxxx Xxxxx ------------------------------------ Name: Xxxxx Xxxxx Title: General Counsel Atlantic Trust Company, N.A. By: /s/ Xxxxxxxx Xxxxxxxxx ------------------------------------ Name: Xxxxxxxx Xxxxxxxxx Title: Ghief Compliance Officer INVESCO Hong Kong Limited By: /s/ Xxxx Xxxxxxxxxxx ------------------------------------ Name: Xxxx Xxxxxxxxxxx Title: Reg. Head of Legal AP INVESCO Asset Management Deutschland GmbH By: /s/ Xxxxxxxxx Xxxxxxxxxx ------------------------------------ Name: Xxxxxxxxx Xxxxxxxxxx Title: Head of Legal CE INVESCO Asset Management Limited By: /s/ Xxxx Xxxxxx ------------------------------------ Name: Xxxx Xxxxxx Title: Director of European Compliance INVESCO Asset Management S.A. By: /s/ Xxxxxxx Xxxxxxx ------------------------------------ Name: Xxxxxxx Xxxxxxx Title: Managing Director INVESCO Asset Management Osterreich GmbH By: /s/ Xxxxxx Xxxxx ------------------------------------ Name: Xxxxxx Xxxxx Title: Managing Director INVESCO Global Asset Management (N.A.), Inc. By: /s/ Xxxxxxx Xxxxx ------------------------------------ Name: Xxxxxxx Xxxxx Title: General Counsel INVESCO Management Company S.A. By: /s/ Xxxx Xxxxxx ------------------------------------ Name: Xxxx Xxxxxx Title: Director of European Compliance INVESCO Management S.A. By: /s/ Xxxxx Xxxxxxxx ------------------------------------ Name: Xxxxx Xxxxxxxx Title: Head of Investment Operations INVESCO Institutional (N.A.), Inc. By: /s/ Xxxxxxx Xxxxx ------------------------------------ Name: Xxxxxxx Xxxxx Title: General Counsel INVESCO Maximum Income Management S.A. By: /s/ Xxxxx Xxxxxxxx ------------------------------------ Name: Xxxxx Xxxxxxxx Title: Head of Investment Operations INVESCO Private Capital, Inc. By: /s/ Xxxxxxx Xxxxx ------------------------------------ Name: Xxxxxxx Xxxxx Title: General Counsel INVESCO Senior Secured Management, Inc. By: /s/ Xxxxxxx Xxxxx ------------------------------------ Name: Xxxxxxx Xxxxx Title: General Counsel INVESCO Taiwan Limited By: /s/ Xxxx Xxxxxxxxxxx ------------------------------------ Name: Xxxx Xxxxxxxxxxx Title: Reg. Head of Legal, AP INVESCO Asset Management (Japan) Limited By: /s/ Xxxx Xxxxxxxxxxx ------------------------------------ Name: Xxxx Xxxxxxxxxxx Title: Reg. Head of Legal, AP INVESCO Asset Management Ireland Limited By: /s/ Xxxxx Xxxxxxxx ------------------------------------ Name: Xxxxx Xxxxxxxx Title: Head of Investment Operations INVESCO Kapitalanlagegesellschaft GmbH By: /s/ Xxxxxxxxx Xxxxxxxxxx ------------------------------------ Name: Xxxxxxxxx Xxxxxxxxxx Title: Head of Legal CE PowerShares Capital Management LLC By: /s/ Xxxxx Xxxxxxxxx ------------------------------------ Name: Xxxxx Xxxxxxxxx Title: General Counsel & COO Xxxxx Xxx Investment Counsel, Inc. By: /s/ Xxxx Xxxxxxxx ------------------------------------ Name: Xxxx Xxxxxxxx Title: General Counsel