UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, DC 20549
SCHEDULE 13G
Under the Securities Exchange Act of 1934
(Amendment No. )*
MDC PARTNERS
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(Name of Issuer)
Common
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(Title of Class of Securities)
55269710
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(CUSIP Number)
December 31, 2008
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(Date of Event Which Requires Filing of this Statement)
Check the appropriate box to designate the rule pursuant to which this
Schedule is filed:
|X| Rule 13d-1(b)
|_| Rule 13d-1(c)
|_| Rule 13d-1(d)
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* The remainder of this cover page shall be filled out for a reporting
person's initial filing on this form with respect to the subject class of
securities, and for any subsequent amendment containing information which
would alter the disclosures provided in a prior cover page.
The information required in the remainder of this cover page shall not be
deemed to be "filed" for the purpose of Section 18 of the Securities Exchange
Act of 1934 or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).
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1. NAME OF REPORTING PERSONS
I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)
William Blair & Company, L.L.C.
36-2214610
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2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
(a) |_|
(b) |_|
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3. SEC USE ONLY
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4. CITIZENSHIP OR PLACE OF ORGANIZATION
222 W Adams
Chicago, IL 60606
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NUMBER OF 5. SOLE VOTING POWER
SHARES 1514972
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BENEFICIALLY 6. SHARED VOTING POWER
OWNED BY -0-
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EACH 7. SOLE DISPOSITIVE POWER
REPORTING 1514972
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PERSON 8. SHARED DISPOSITIVE POWER
WITH -0-
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9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
1514972
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10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*
|_|
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11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
5.55
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12. TYPE OF REPORTING PERSON*
BD, IA
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*SEE INSTRUCTIONS BEFORE FILLING OUT!
Item 1(a). Name of Issuer:
MDC PARTNERS
Item 1(b). Address of Issuer's Principal Executive Offices:
45 Hazelton Ave
Toronto, ON M5R2E3
Item 2(a). Name of Person Filing:
William Blair & Company, L.L.C.
Item 2(b). Address of Principal Business Office, or if None, Residence:
222 W Adams
Chicago, IL 60606
Item 2(c). Citizenship:
U.S.A.
Item 2(d). Title of Class of Securities:
Common
Item 2(e). CUSIP Number:
55269710
Item 3. If This Statement is Filed Pursuant to Rule 13d-1(b), or 13d-2(b)
or (c), Check Whether the Person Filing is a:
(a) |X| Broker or dealer registered under Section 15 of 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.
(e) |X| An investment adviser in accordance with Rule
13d-1(b)(1)(ii)(E);
(f) |_| An employee benefit plan or endowment fund in accordance with
Rule 13d-1(b)(1)(ii)(F);
(g) |_| A parent holding company or control person in accordance with
Rule 13d-1(b)(1)(ii)(G);
(h) |_| A savings association as defined in Section 3(b) of the
Federal Deposit Insurance Act;
(i) |_| A 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).
Item 4. Ownership.
Provide the following information regarding the aggregate number and
percentage of the class of securities of the issuer identified in Item 1.
(a) Amount beneficially owned: 1514972
(b) Percent of class: 5.55
(c) Number of shares as to which such person has:
(i) Sole power to vote or to direct the vote
1514972
(ii) Shared power to vote or to direct the vote
-0-
(iii) Sole power to dispose or to direct the disposition of
1514972
(iv) Shared power to dispose or to direct the disposition of
-0-
Item 5. Ownership of Five Percent or Less of a Class.
If this statement is being filed to report the fact that as of the date
hereof the reporting person has ceased to be the beneficial owner of more than
five percent of the class of securities check the following |_|.
Item 6. Ownership of More Than Five Percent on Behalf of Another Person.
Item 7. Identification and Classification of the Subsidiary Which Acquired the
Security Being Reported on by the Parent Holding Company or Control
Person.
Item 8. Identification and Classification of Members of the Group.
Item 9. Notice of Dissolution of Group.
Item 10. Certifications.
By signing below I certify that, to the best of my knowledge and
belief, the securities referred to above were acquired and are held in
the ordinary course of business and were not acquired and 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 such 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.
January 12, 2009
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(Date)
/s/ Michelle Seitz
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(Signature)
Principal & Manager of Investment Services
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(Name/Title)
The original statement shall be signed by each person on whose behalf the
statement is filed or his authorized representative. If the statement is signed
on behalf of a person by his authorized representative other than an executive
officer or general partner of the filing person, evidence of the
representative's authority to sign on behalf of such person shall be filed with
the statement, provided, however, that a power of attorney for this purpose
which is already on file with the Commission may be incorporated by reference.
The name and any title of each person who signs the statement shall be typed or
printed beneath his signature.
NOTE: Schedules filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See 240.13d-7 for other parties
for whom copies are to be sent.
Attention: Intentional misstatements or omissions of fact constitute Federal
criminal violations (See 18 U.S.C. 1001)