| Top Institutional Holders |
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| Holder | Shares | % Out | Value* | Reported |
|---|
| Vanguard Group, Inc. (The) | 2,621,686 | 2.91 | 15,913,634 | Mar 31, 2013 | | FMR, LLC | 2,393,254 | 2.65 | 14,527,051 | Mar 31, 2013 | | Baker Brothers Advisors, LLC | 1,638,871 | 1.82 | 9,947,946 | Mar 31, 2013 | | BlackRock Fund Advisors | 1,056,639 | 1.17 | 6,413,798 | Mar 31, 2013 | | Wall Street Associates | 984,300 | 1.09 | 5,974,701 | Mar 31, 2013 | | State Street Corporation | 632,762 | 0.70 | 3,840,865 | Mar 31, 2013 | | Northern Trust Corporation | 610,274 | 0.68 | 3,704,363 | Mar 31, 2013 | | BlackRock Institutional Trust Company, N.A. | 517,784 | 0.57 | 3,142,948 | Mar 31, 2013 | | Morgan Stanley | 517,763 | 0.57 | 3,142,821 | Mar 31, 2013 | | Deutsche Bank Aktiengesellschaft | 400,702 | 0.44 | 2,432,261 | Mar 31, 2013 |
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| Holder | Shares | % Out | Value* | Reported |
|---|
| Fidelity Select Portfolios - Biotechnology | 1,481,266 | 1.64 | 7,776,646 | Apr 30, 2013 | | Vanguard Small-Cap Index Fund | 979,033 | 1.09 | 5,942,730 | Mar 31, 2013 | | Fidelity Small Cap Growth Fund | 800,000 | 0.89 | 4,488,000 | Jan 31, 2013 | | iShares Russell 2000 Index Fund | 644,345 | 0.71 | 3,382,811 | Apr 30, 2013 | | Vanguard Total Stock Market Index Fund | 539,675 | 0.60 | 3,275,827 | Mar 31, 2013 | | Vanguard Extended Market Index Fund | 478,569 | 0.53 | 2,904,913 | Mar 31, 2013 | | Vanguard Small-Cap Growth Index Fund | 479,161 | 0.53 | 2,908,507 | Mar 31, 2013 | | iShares Russell 2000 Growth Index Fund | 284,994 | 0.32 | 1,496,218 | Apr 30, 2013 | | Spartan Extended Market Index Fund | 207,004 | 0.23 | 1,086,771 | Apr 30, 2013 | | College Retirement Equities Fund-Stock Account | 183,602 | 0.20 | 1,114,464 | Mar 31, 2013 |
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View Transactions for Insiders & Institutional Holders Value shown is computed using the security's price on the report date given. Currency in USD. |