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It takes an average of about 11-12 years for a film industry worker to become a professional at directing film or television

Analysis: to figure out the average (mean) length of time a filmmaker will work until becoming a professional director. I was also interested in their career background before reaching a professional status since there seems to be little information on this elsewhere.

I collected data from the Internet Movie Database (IMDb.com) to complete a simple analysis of the queries noted above -- its resulting data is shown below. I defined "timespan" as the difference between a filmmaker's earliest credit on IMDb and their first professional directorial debut, and omitted timespans less than 3 years due to insufficient information. I defined "professional" by an amount of IMDb ratings (>50).

Findings: Although the number of entries is 184 directors, and therefor not statistically significant (it's time consuming doing this manually), it is still clear that a few patterns emerge: first, the average time to become a professional director is about 11.5 years. Second, the most common careers before becoming professional were: 

1) Actor

2) Short Film / Music Video Director

3) Assistant Director

With Producer next, and the rest roughly tying for fifth.

Conclusion: It's important to note these are likely conservative estimates since not everyone has their early careers ledgered accurately within IMDb. In any case, for anyone wishing to become a professional director it seems the most efficient manner of doing so is by creating short films and music videos (since this method has the highest percentage-to-time ratio, nearly 2:1).

Industry Job
Notable Directing Credit
Tom CavanaghActor12Flash
Timothy Van PattenActor14Game of Thrones
Steve ShillActor7Flash
Steve ShillActor7The Wire
Robert Duncan McNeilActor19Supernatural
Richard Speight Jr.Actor16Supernatural
Matt ShakmanActor18Game of Thrones
Jensen AcklesActor15Supernatural
Jack BenderActor10Game of Thrones
Gregory SmithActor21Flash
Dominic WestActor17The Wire
Clark JohnsonActor11The Wire
Chales HaidActor17Breaking Bad
Brian CranstonActor31Breaking Bad
Antonio NegretActor7Flash
Amanda TappingActor13Supernatural
Charlie McDowellActor10Silicon Valley
Matt RossActor18Silicon Valley
Marc BucklandActor9Scrubs
Will MackenzieActor13Scrubs
John PutchActor23Scrubs
Zach BraffActor15Scrubs
Michael MacdonaldActor7Scrubs
Joanna KernsActor17Scrubs
Paul QuinnActor8Scrubs
Ted WassActor15Scrubs
Marielle HellerActor14Beautiful Day in the Neighbourhood
Olivia WildeActor25Booksmart
Henry Ian CusickActor24The 100
Antonio NegretActor / Writer8The 100
Tim AndrewAD3Supernatural
Terry IngramAD8TV Movies
Tara Nicole WeyrAD12Flash
Phil ChiperaAD22Flash
Peter MedakAD5Breaking Bad
Mike RohlAD8Supernatural
Michael A. AllowitzAD15Flash
Kim MannersAD8Supernatural
Kevin ParksAD20Supernatural
John MacCarthyAD14Supernatural
J. Miller TobinAD11Supernatural
Ed BianchiAD3The Wire
Douglas AarniokoskiAD12Flash
David McWhirterAD17Flash
Daniel AttiasAD7The Wire
Charles BeesonAD8Supernatural
Brent CrowellAD14Flash
Anthony HemingwayAD10The Wire
Richard A. WellsAD12Scrubs
Mairzee AlmasAD7The 100
Omar MadhaAD4The 100
Ian SamoilAD19The 100
James L. ConwayAD/Producer3Supernatural
Stephen SurjikArt Department7Flash
Terry McDonoughCam-Op14Breaking Bad
Guy Norman BeeCam-Op11Supernatural
Colin BuckseyCam-Op3Breaking Bad
Kevin TancharoenChoreographer3Flash
Matthew DiamondChoreographer3Scrubs
Bronwen HughesDirector Assistant5Breaking Bad
Serge LadouceurDOP10Supernatural
Phil AbrahamDOP25Breaking Bad
Michael SlovisDOP16Breaking Bad
John BehringDOP7Flash
James HeadDOP10TV Movies
Glen WinterDOP9Flash
Felix Enriquez AlcalaDOP7Breaking Bad
Ernest R. DickersonDOP8The Wire
Dermott DownsDOP10Flash
C. Kim MilesDOP17Flash
Alex ZakrzewskiDOP11The Wire
Michael SpillerDOP15Scrubs
John InwoodDOP15Scrubs
Victor Nelli Jr.DOP15Scrubs
Uta BriesewitzDOP14The 100
Michael C. BlundellDOP31The 100
Wendey StanzlerEditor15Flash
Viet NguyenEditor15Flash
Philip SgricciaEditor4Supernatural
Kevin MockEditor4Flash
John F. ShowalterEditor24Supernatural
Harry JierjianEditor13Flash
Elodie KeeneEditor10The Wire
Daniel SackheimEditor11Game of Thrones
Chris PeppeEditor17Flash
Bert KishEditor4TV Movies
Tim RocheEditor15Silicon Valley
John MichelEditor28Scrubs
Rick BlueEditor18Scrubs
Henry ChanEditor12Scrubs
John F. ShowalterEditor24The 100
Matt BarberEditor10The 100
Rob HardyFeature Filmmaker6Flashstarted with feature film
Kevin SmithFeature Filmmaker3FlashSuccessful indie feature: Clerks
Eduardo SanchezFeature Filmmaker7SupernaturalSuccessful indie feature: Blair Witch
Brad AndersonFeature Filmmaker3The WireStarted with feature film
Rob J GreenleaKey Grip24Flash
Stefan PleszczynskiLocation Manager6Flash
Milcho ManchevskiMusic Videos9The Wire
Leslie LibmanMusic Videos13The Wire
John DahlMusic Videos4Breaking Bad
Johan RenckMusic Videos9Breaking Bad
Jim McKayMusic Videos6Breaking Bad
David SladeMusic Videos11Breaking BadSuccessful indie feature: Hard Candy - Drama
Adam BernsteinMusic Videos6Breaking Bad
Peter LauerMusic Videos6Scrubs
Scott WinantProducer6Breaking Bad
Robert SingerProducer16Supernatural
Robert ColesberryProducer27The Wire
D.B. WeissProducer5Game of Thrones
Craig ZiskProducer8Scrubs
Randall Keenan WinstonProducer11Scrubs
Jeff MelmanProducer12Scrubs
Jason EnslerProducer5Scrubs
Jay AlaimoProducer6Scrubs
Dean WhiteProducer18The 100
Tim ScanlanProducer13The 100
Steve DePaulProducer7
Rachel TalalayProducer / Accountant10Flash
Lawrence TrillingProducer / Actor10Scrubs
Milan CheylovProducer / Actor10The 100
Tricia BrockProducer / Writer25Breaking Bad
John ShibanProducer / Writer7Breaking Bad
Mark StegemannProducer / Writer10Scrubs
Rob GreenbergProducer / Writer12Scrubs
Michelle MacLarenProducer /PM12Breaking Bad
Nina Lopez-CorradoProducer Assistant8Supernatural
Alice TroughtonProducer Assistant4Flash
Jerry WanekProduction Designer19Supernatural
Thomas J. WrightProduction Ilustrator19Supernatural
Josh PodeswaProduction Manager10Game of Thrones
Alik SakharovProduction Manager22Game of Thrones
Linda MendozaProduction Supervisor8Scrubs
Alexandra La RocheScript Supervisor17Flash
Jamie BabbitScript Supervisor3Silicon Valley
Gail MancusoScript Supervisor12Scrubs
Thor FreudenthalShort Filmmaker13Flash
Seith MannShort Filmmaker5The Wire
Scott KeckenShort Filmmaker16The Wire
Rian JohnsonShort Filmmaker9Breaking Bad
Rashaad Ernesto GreenShort Filmmaker7SupernaturalSuccessful indie feature: Gun Hill Road
Neil MarshallShort Filmmaker10Game of Thrones
Millicent SheltonShort Filmmaker8Flash
Laura BelseyShort Filmmaker9Flash
Jesse WarnShort Filmmaker4Flash
Hanelle M. CulpepperShort Filmmaker12Flash
Clement VirgoShort Filmmaker3The Wire
Brian KirkShort Filmmaker6Game of Thrones
Amyn KaderaliShort Filmmaker11SupernaturalSuccessful indie feature: Kissing Cousins
Alan TaylorShort Filmmaker5Game of Thrones
Agnieszka HollandShort Filmmaker9The Wire
David YatesShort Filmmaker6Harry Potter Films
Liza JohnsonShort Filmmaker13Silicon Valley
Maggie CareyShort Filmmaker10Silicon ValleyComedy/drama
Gillian RobespierreShort Filmmaker6Silicon Valley
Pete ChatmonShort Filmmaker6Silicon Valley
Ed FraimanShort Filmmaker3The 100
David PlattSound Mixer20The Wire
Clay TarverSoundtrack7Silicon ValleyChavez band member in 1991
Mark MylodStage Manager6Game of Thrones
Ken WhittinghamStage Manager10Scrubs
Miguel SapochnikStoryboard Artist14Game of Thrones
Steve BoyumStunt Coordinator23Supernatural
J.J. MakaroStunt Coordinator31Flash
Ralph Hemeckertitle Sequence Creator5Flash
Armen V. KevorkianVFX Coordinator17Flash
Vince GilliganWriter7Breaking BadCreator of Breaking Bad
Thomas SchnauzWriter11Breaking Bad
Peter GouldWriter6Breaking Bad
Joy KeckenWriter16The Wire
George MastrasWriter6Breaking Bad
Eric KripkeWriter10Supernatural
David BenioffWriter11Game of Thrones
Daniel MinahanWriter5Game of Thrones
Christie Will WolfWriter10TV Movies
Ben EdlundWriter10Supernatural
Alec BergWriter16Silicon Valley
Eric AppelWriter6Silicon Valley
Bill LawrenceWriter11Scrubs
Celine SciammaWriter3Portrait of a Lady on Fire
Sam CatlinWriter / Actor15Breaking Bad
Elen CelebogluWriter / Director Assistant6Scrubs
Niki CaroWriter6Mulan