Mark Zuckerberg's net worth took a pretty big hit the past week, as investigators reviewed Facebook's bungled IPO and the company's shares slid farther and farther below their offering price.

Shares of Facebook fell below $29 yesterday for the first time, and the company's co-founder and CEO saw his fortune tumble right along with it. According to Bloomberg, Zuck's 503.6 million shares are now worth $14.7 billion, which knocks him off Bloomberg's Billionaire's Index of the 40 wealthiest individuals in the world.

Facebook began trading publicly on May 18. When the market closed that day, the company's stock was valued at $38.23, up just $0.23 cents from its offering price. Zuck's net worth jumped slightly from $19.1 billion to $19.4 billion during the day.

As of Wednesday morning, Colombia's Luis Carlos Sarmiento held the number-40 spot on Bloomberg's list, with an estimated net worth of $15.5 billion.

Zuck, who married college sweetheart Priscilla Chan the day after Facebook's Nasdaq debut, doesn't seem to be wringing his hands over his billions. The couple was recently spotted honeymooning in Rome, Italy, where they enjoyed local landmarks like the Sistine Chapel and even made a quick stop at McDonald's.

The couple is known for keeping a low profile and opting for casual attire in public. Zuck, for one, dons a hooded sweatshirt more often than a three-piece suit, and Priscilla has been seen wearing a small ruby ring instead of a large diamond on her ring finger.

Writing on Quora, a man who identifies himself as former Facebook employee Ezra Callahan (2004 - 2010) explains Zuckerberg's attitude toward wealth:

I can tell you that when I worked with Mark Zuckerberg, money was certainly not his primary motivator. He lived an absurdly spartan lifestyle. Well after the point that Facebook's valuation passed $1B, Mark still lived in a small, crappy apartment and slept on a mattress on the floor. All he really cared about was work and he spent most of his waking hours at the office, so it didn't seem to matter much to him to furnish his apartment or spend money on much of anything (food, clothes...anything really).

As Facebook's stock continues to fluctuate, Zuck probably won't be losing a lot of sleep over his fortune.

Also on HuffPost:

Flip through the gallery to see Mark Zuckerberg in some of his most casual attire.
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  • Sheryl Sandberg

    Chief Operating Officer at Facebook <a href="http://www.facebook.com/sheryl" target="_hplink">http://www.facebook.com/sheryl</a>

  • Reed Hastings

    CEO of Netflix <a href="http://www.facebook.com/reed1960" target="_hplink">http://www.facebook.com/reed1960</a>

  • Kevin Systrom

    CEO of Instagram <a href="https://www.facebook.com/systrom" target="_hplink">https://www.facebook.com/systrom</a>

  • Alexia Tsotsis

    Co-Editor at TechCrunch <a href="http://www.facebook.com/alexiatsotsis" target="_hplink">http://www.facebook.com/alexiatsotsis</a> *Note: TechCrunch and Huffington Post are both part of Aol.

  • Eduardo Saverin

    Co-founder of Facebook <a href="http://www.facebook.com/saverin" target="_hplink">http://www.facebook.com/saverin</a>

  • Kevin Rose

    Sr. Product Manager at Google <a href="http://www.facebook.com/kevinrose" target="_hplink">http://www.facebook.com/kevinrose</a>

  • Randi Zuckerberg

    Founder/CEO at R to Z Media Formerly led consumer marketing at Facebook <a href="http://www.facebook.com/randi" target="_hplink">http://www.facebook.com/randi</a>

  • Pete Cashmore

    Founder/CEO of Mashable <a href="http://www.facebook.com/petecashmore" target="_hplink">http://www.facebook.com/petecashmore</a>

  • Nick Bilton

    Tech Columnist at The New York Times <a href="http://www.facebook.com/nickbilton" target="_hplink">http://www.facebook.com/nickbilton</a>

  • Sean Parker

    Director at Spotify <a href="http://www.facebook.com/Sean" target="_hplink">http://www.facebook.com/Sean</a>

  • Liz Gannes

    Senior Writer at All Things D <a href="http://www.facebook.com/LizGannes" target="_hplink">http://www.facebook.com/LizGannes</a>

  • Bret Taylor

    Chief Technology Officer at Facebook <a href="http://www.facebook.com/btaylor" target="_hplink">http://www.facebook.com/btaylor</a>

  • Steve Wozniak

    Co-founder of Apple <a href="http://www.facebook.com/stevewoz" target="_hplink">http://www.facebook.com/stevewoz</a>

  • Laurie Segall

    Tech Reporter at CNN Money <a href="http://www.facebook.com/LaurieSegall" target="_hplink">http://www.facebook.com/LaurieSegall</a>

  • Anthony De Rosa

    Social Media Editor at Reuters <a href="http://www.facebook.com/antderosa" target="_hplink">http://www.facebook.com/antderosa</a>

  • Loic Le Meur

    Founder/CEO of Seesmic <a href="http://www.facebook.com/loic" target="_hplink">http://www.facebook.com/loic</a>

  • Om Malik

    Founder and Senior Writer at GigaOm <a href="http://www.facebook.com/ommalik" target="_hplink">http://www.facebook.com/ommalik</a>

  • Jennifer Van Grove

    Writer at VentureBeat <a href="http://www.facebook.com/jbruin" target="_hplink">http://www.facebook.com/jbruin</a>

  • Blake Ross

    Director of Product at Facebook <a href="http://www.facebook.com/blake" target="_hplink">http://www.facebook.com/blake</a>

  • Michael Arrington

    Founder at TechCrunch <a href="http://www.facebook.com/theuncrunched" target="_hplink">http://www.facebook.com/theuncrunched</a> *Note: TechCrunch and Huffington Post are both part of Aol.

  • Rosa Golijan

    Senior Writer/Editor at msnbc.com <a href="http://www.facebook.com/rosa" target="_hplink">http://www.facebook.com/rosa</a>

  • Ben Parr

    Co-Founder at The Peep Project <a href="http://www.facebook.com/ben.parr" target="_hplink">http://www.facebook.com/ben.parr</a>

  • Mathew Ingram

    Senior Writer at GigaOm <a href="http://www.facebook.com/mathewingram" target="_hplink">http://www.facebook.com/mathewingram</a>

  • Walt Mossberg

    Tech Columnist at The Wall Street Journal <a href="http://www.facebook.com/WaltMossberg" target="_hplink">http://www.facebook.com/WaltMossberg</a>

  • Robert Scoble

    Tech Blogger, Startup Liaison Officer at Rackspace <a href="http://www.facebook.com/RobertScoble" target="_hplink">http://www.facebook.com/RobertScoble</a>

  • Guy Kawasaki

    Co-founder at Alltop <a href="http://www.facebook.com/guy" target="_hplink">http://www.facebook.com/guy</a>

  • Eric Eldon

    Editor at TechCrunch <a href="http://www.facebook.com/EricEldon" target="_hplink">http://www.facebook.com/EricEldon</a> *Note: TechCrunch and Huffington Post are both part of Aol.

  • Jolie O'Dell

    Writer at VentureBeat <a href="http://www.facebook.com/jolieodell" target="_hplink">http://www.facebook.com/jolieodell</a>

  • Dennis Crowley

    Founder/CEO of Foursquare <a href="http://www.facebook.com/dens" target="_hplink">http://www.facebook.com/dens</a>

  • Danny Sullivan

    Editor-In-Chief, Search Engine Land <a href="http://www.facebook.com/dannysullivan" target="_hplink">http://www.facebook.com/dannysullivan</a>

  • Kara Swisher

    Co-executive Editor at All Things Digital <a href="http://www.facebook.com/KaraSwisher" target="_hplink">http://www.facebook.com/KaraSwisher</a>

  • Leo Laporte

    Tech Podcaster/Pundit <a href="http://www.facebook.com/leoglaporte" target="_hplink">http://www.facebook.com/leoglaporte</a>

  • Alexander Howard

    Gov 2.0 Washington Correspondent at O'Reilly Media <a href="http://www.facebook.com/alexhoward" target="_hplink">http://www.facebook.com/alexhoward</a>

  • Richard MacManus

    Founder/Editor at ReadWriteWeb <a href="http://www.facebook.com/ricmac" target="_hplink">http://www.facebook.com/ricmac</a>

  • Joshua Topolsky

    Editor-in-Chief of The Verge <a href="http://www.facebook.com/joshuatopolsky" target="_hplink">http://www.facebook.com/joshuatopolsky</a>

  • Gary Vaynerchuk

    Video Blogger, Author/Speaker on Brands/Social Media <a href="http://www.facebook.com/profile.php?id=708727040" target="_hplink">http://www.facebook.com/profile.php?id=708727040</a>

  • Liz Heron

    Social Media Director at The Wall Street Journal <a href="http://www.facebook.com/lheron" target="_hplink">http://www.facebook.com/lheron</a>

  • Craig Newmark

    Founder of Craigslist <a href="http://www.facebook.com/craignewmark" target="_hplink">http://www.facebook.com/craignewmark</a>

  • Jonah Peretti

    Co-founder/CEO of Buzzfeed Co-founder of The Huffington Post <a href="http://www.facebook.com/peretti" target="_hplink">http://www.facebook.com/peretti</a>

  • Kate O'Neill

    Product Marketing at Facebook <a href="http://www.facebook.com/kkoneill" target="_hplink">http://www.facebook.com/kkoneill</a>

  • MG Siegler

    General Partner at CrunchFund <a href="http://www.facebook.com/parislemon" target="_hplink">http://www.facebook.com/parislemon</a>

  • Zee Kane

    CEO at The Next Web <a href="http://www.facebook.com/zee" target="_hplink">http://www.facebook.com/zee</a>

  • Susan Beebe

    Chief Listener at Dell <a href="http://www.facebook.com/susan.beebe" target="_hplink">http://www.facebook.com/susan.beebe</a>

  • Vadim Lavrusik

    Journalist Program Manager at Facebook <a href="http://www.facebook.com/vadim" target="_hplink">http://www.facebook.com/vadim</a>

  • Gina Trapani

    Founder at LifeHacker <a href="http://www.facebook.com/ginatrapani" target="_hplink">http://www.facebook.com/ginatrapani</a>

  • Larry Magid

    Co-director at ConnectSafely.org <a href="http://www.facebook.com/larrymagid" target="_hplink">http://www.facebook.com/larrymagid</a>

  • Matt Buchanan

    BuzzFeed Tech Editor <a href="http://www.facebook.com/mattbuchanan" target="_hplink">http://www.facebook.com/mattbuchanan</a>

  • Soraya Darabi

    Founder of Foodspotting <a href="http://www.facebook.com/sorayadarabi" target="_hplink">http://www.facebook.com/sorayadarabi</a>

  • Dave Morin

    Co-founder/CEO of Path <a href="http://www.facebook.com/dvmrn" target="_hplink">http://www.facebook.com/dvmrn</a>

  • Mark Zuckerberg

    Co-founder/CEO at Facebook <a href="http://www.facebook.com/zuck" target="_hplink">http://www.facebook.com/zuck</a>