UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment) Macerich Co. (Name of Issuer) Ordinary Shares (Title of Class of Securities) 554382101 (CUSIP Number) December 31, 2010 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which this Schedule is filed: xRule 13d-1(b) Rule 13d-1(c) Rule 13d-1(d) 1. NAME OF REPORTING PERSONS ING Clarion Real Estate Securities, LLC. 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) (b) Not Applicable 3. SEC USE ONLY 4. CITIZENSHIP OR PLACE OF ORGANIZATION Organized in the state of Delaware NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH: 5.SOLE VOTING POWER 5,747,357 6. SHARED VOTING POWER 5,680 7. SOLE DISPOSITIVE POWER 12,038,614 8. SHARED DISPOSITIVE POWER 0 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 12,038,614 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES 0 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 9.25% 12. TYPE OF REPORTING PERSON IA Item 1(a). Name of Issuer: Macerich Co. Item 1(b). Address of Issuer's Principal Executive Offices: 401 Wilshire Blvd., Suite 700 Santa Monica, CA 90401 Item 2(a). Name of Person Filing: ING Clarion Real Estate Securities, LLC. Item 2(b). Address of Principal Business Office or, if None, Residence: ING Clarion Real Estate Securities, LLC. 201 King of Prussia Road Suite 600 Radnor, PA 19087 Item 2(c). Citizenship: See item 4 on Page 2 Item 2(d). Title of Class of Securities: Ordinary Shares Item 2(e). CUSIP Number: 554382101 Item 3. If this statement is filed pursuant to Rules 13d-1(b), or 13d-2(b) or (c), check whether the person filing is a: (Not Applicable) (a) Broker or dealer registered under Section 15 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"); (b) Bank as defined in Section 3(a)(6) of the Exchange Act; (c) Insurance company as defined in Section 3(a)(19) of the Exchange Act; (d) Investment company registered under Section 8 of the Investment Company Act of 1940, as amended (the "Investment Company Act"); x(e) Investment adviser in accordance with Rule 13d 1(b)(1)(ii)(E) under the Exchange Act; (f) Employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F) under the Exchange Act; (g) Parent holding company or control person in accordance with Rule 13d-1(b)(ii)(G) under the Exchange Act; (h) Savings association as defined in Section 3(b) of the Federal Deposit Insurance Act; (i) Church plan that is excluded from the definition of an investment company under Section 3(c)(14) of the Investment Company Act; (j) Group in accordance with Rule 13d-1(b)(1)(ii)(J) under the Exchange Act. Item 4. Ownership. (a) Amount beneficially owned: See item 9 on Page 2 (b) Percent of class: See item 11 on Page 2 (c) Number of shares as to which such person has: (i) Sole power to vote or to direct the vote: See item 5 on Page 2 (ii) Shared power to vote or to direct the vote: See item 6 on Page 2 (iii) Sole power to dispose or to direct the disposition of: See item 7 on Page 2 (iv) Shared power to dispose or to direct the disposition of: See item 8 on Page 2 Item 5. Ownership of Five Percent or Less of a Class. Not Applicable Item 6. Ownership of More than Five Percent on Behalf of Another Person. Not Applicable Item 7. Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person. Not Applicable Item 8. Identification and Classification of Members of the Group. Not Applicable Item 9. Notice of Dissolution of Group. Not Applicable Item 10. Certification. By signing below we certify that, to the best of our knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect. SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. ING CLARION REAL ESTATE SECURITIES, LLC. By: /s/ Robert S Tull (Signature) Robert S Tull Chief Compliance Officer (Name/Title)