By Jonathan Moreland, founder of Insider Insights and author of Profit From Legal Insider Trading.

NEW YORK ( TheStreet) -- Which insiders are selling and buying chunks of stocks?

Below are lists of the top 10 mainly open-market insider purchases and sales filed at the Securities and Exchange Commission Monday, May 16, 2011 as ranked by dollar value. Company executives and directors are in the best position to assess the attractiveness of their firms' shares, and here is how many of them are voting their wallets! Please note, however, that these are factual lists, not buy and sell recommendations. Dollar value is only one metric to assess the importance of an insider transaction.

Transdigm (TDG) Small Robert J DIR 67,430 $5,628,382
Celera (CRA) Quest Diagnostics BO 100,000 $805,680
Geeknet (GKNT) Georgescu Peter A DIR 20,201 $534,640
NiSource (NI) Nutter Wallace Lee DIR 25,000 $507,500
Geo Group (GEO) Zoley George C CB,CEO
12,000 $309,799
Dana Holding (DAN) Wood Roger PR,CEO
16,700 $298,828
Exar (EXAR) Soros Fund Management BO 36,561 $240,614
Kronos Worldwide (KRO) Watson Steven L VCB,CEO
4,200 $227,920
Friendfinder Networks (FFN) Bell Marc H CEO,PR
30,002 $227,103
Friendfinder Networks (FFN) Staton Daniel C CB,TR
29,998 $227,073
Microsoft (MSFT) Gates William H DIR 5,000,000 $126,216,496
Aircastle (AYR) Fortress Investment Group BO 5,000,000 $65,350,000
Cinemark Holdings (CNK) Mitchell Lee Roy DIR 2,000,000 $41,400,000
Validus Holdings (VR) Singh Alok DIR 325,465 $10,486,320
Perrigo (PRGO) Arkin Moshe DIR 107,195 $9,374,221
Broadsoft Inc (BSFT) Deer IV & Co BO 191,000 $7,702,064
Tutor Perini (TPC) Tutor Ronald N CB,CEO
346,200 $7,650,169
Ventas (VTR) Prometheus Senior Quarters BO 313,449 $7,156,163
Bank Of The Ozarks (OZRK) Gleason George G Ii CB,CEO
86,100 $4,160,508
Rackspace Hosting (RAX) Weston Graham M CB,DIR
100,000 $4,133,360

Key to Titles: A=Assistant, AI=Affiliated Investor, AO=Accounting Officer, BD=Business Development, BO=Beneficial Owner, CAO=Chief Accounting Officer, CB=Chairman, CCO=Chief Compliance Officer, CEO=Chief Executive Officer, CFO=Chief Financial Officer, CIO=Chief Information Officer, CO=Compliance Officer, COO=Chief Operating Officer, CT=Controller, CTO=Chief Technology Officer, DIR=Director, EVP=Executive Vice President, F=Founder, FO=Financial Officer, GC=General Counsel, HR=Human Resources, IO=Information Officer, IR=Investor Relations, LO=Legal Officer, MD=Managing Director, O=Officer, OO=Operating Officer, PR=President, PT=Partner, REL=Relative of an insider, SEC=Secretary, SH=Shareholder, SO=Sales Officer, TO=Technology Officer, TR=Treasurer, TT=Trustee, VCB=Vice Chairman, VP=Vice President, X=Ex Officer or other title displayed.
Jonathan Moreland is the founder of, which produces a weekly newsletter and offers professional screening and alerting tools to analyze a proprietary, real-time insider data feed. He is also the principal of Insider Asset Management, a registered investment advisor in New York. Mr. Moreland has been analyzing insider data professionally for two decades and has been a contributor to since 2001. A fundamental analyst with an MBA in finance, Mr. Moreland long ago identified insider data as an excellent first screen to determine where to focus his research efforts. He is quoted frequently in the media for his insider analysis and stock recommendations stemming from it. He is also author of Profit From Legal Insider Trading.

Under no circumstances does the information in this column represent a recommendation to buy or sell stocks. While he cannot provide investment advice or recommendations, Moreland appreciates your feedback; click here to send him an email.