A reasonably complete analysis of the coinmarketcap pages stored on archive.org suggests that it's closer to 30%.

List of “decapped” coins (no longer listed on coinmarketcap), each with a hyperlink to the corresponding bct thread.

• 1Coin (ONE)
• 10kcoin (10k)
• 365Coin (365)
• Abundancecoin (ABC)
• Achillescoin (ACH)
• Aerocoin (AERO)
• Aidbitcoin (AID)
• Aimcoin (AIM)
• Aircoin (AIR)
• Alipaycoin (ALI)
• Altcoin (ATC)
• APIcoin (XAP)
• Arcoin (AR)
• Ascentcoin (ASCE)
• Astrocoin (ASR)
• B1bl3Coin (B1BL3)
• Badgercoin (BDG)
• Banknote (BN)
• Bcttalkcoin (BCT)
• BigBullioncoin (BIG)
• BillionCoin (BIL)
• BitBlockcoin (BBL)
• Bitleu (BTL)
• BitLion (XBL)
• Bitmiles (BTMI)
• BitMocoin (XBM)
• Bitmoneycoin (BMY)
• BitsharesX (BTSX)
• BlackTokencoin (BLKT)
• BlitzCoin (BLTZ)
• Bluechip (BCH)
• Bollywoodcoin (BDC)
• Bones (BONES)
• Bongger (BGR)
• BonusCoin (BNS)
• BoschiCoin (BCC)
• Burnercoin (BURN)
• CaiShen Coin (CAI)
• CaliforniaCoin (CAC)
• Candycoin (YUM)
• CHC coin (CHCC)
• Chococoin (CCC)
• CoCoCoin (COCO)
• CoffeeCoin (CFC2)
• Coinmarketscoin (JBS)
• Colbertcoin (CC)
• CornerstoneCoin (CCX)
• Credits (CR)
• Cryptogenic Bullion (CGB)
• CryptoMETH (METH)
• Cryptostuds (CSD)
• CScoin (CSO)
• Czarcoin (CZR)
• DarkFoxcoin (DRX)
• DarkGold (DGD)
• DarkKush (DANK)
• DarkPeer (DPC)
• Darkswift (DS)
• DeafDollars (DEAF)
• Deepcoin (DCN)
• DigitalCommercecoin (DCM)
• Diode (DIO)
• Distrocoin (DISTRO)
• DogeBlackCoin (DOGEBC)
• DolphinCoin (DOLP)
• Doomcoin (DOOM)
• Doscoin (DOS)
• DoubleEaglecoin (XDE)
• Dreamcoin (DRM)
• EMoney (ECASH)
• EBTCoin (EBT)
• Ekitacoin (EKITA)
• ElectricCoin (VOLT)
• Elitecoin (ELITE)
• Emoticoin (EMO)
• Emucoin (EMU)
• EntropyCoin (ENC)
• ESportsCoin (ESC)
• Ethancoin (ETHAN)
• EthereumDark (ETD)
• eToken (ETOK)
• Euphoriacoin (EUPH)
• eUtopiumCoin (UPM)
• Extractcoin (XTR)
• Findcoin (FIND)
• Firecoin (FIRE)
• Flexiblecoin (FLEX)
• Forexcoin (FRX)
• FoxCoin (FOX)
• FrozenCoin (FZ)
• Frycoin (FRY)
• FUDcoin (FUD)
• Functioncoin (FCC)
• Gaelcoin (GAC)
• Gameleaguecoin (GML)
• GamersCoin (GMC)
• Ganjacoin (GANJA)
• Gapcoin (GAP)
• GB Coin (GBC)
• Germanycoin (GER)
• Ghostcoin (GHC)
• GhostCoin (GHOST)
• Global Denomination (GDN)
• GlobalBoost (BST)
• Globe (GLB)
• GlowCoin (GLOW)
• Gnosiscoin (GNS)
• Goalcoin (GOAL)
• Grain (GRA)
• Gridcoin Classic (GRCX)
• Groupcoin (GPC)
• Growcoin (GROW)
• GrowthCoin (GRW)
• Grumpycoin (GRUMP)
• Harmonycoin (HMY)
• HighFiveCoin (H5C)
• Hotcoin (HOT)
• Huskycoin (HC)
• Hypercoin (HYC)
• Incogcoin (ICG)
• InkWayCoin (LKNX)
• Instantcoin (BTI)
• Intellect (ITL)
• Intellicoin (INT)
• Isiscoin (ISIS)
• JupiterCoin (JPC)
• KarpelesCoin (KAR)
• KashmirCoin (KSC)
• Kimdotcoin (DOT)
• Kingdomcoin (KING)
• Kryptonite (KRYP)
• Latium (LAT)
• LeagueCoin (LOL)
• Lebowskis (LBW)
• Leprocoin (LPC)
• Limecoin lite (LCL)
• LionCoin (LION)
• Litecoinplus (XLC)
• Logicoin (LGC)
• LottoShares (LTS)
• MACDcoin (MACD)
• Magicoin (MAGIC)
• MaiaCoin (MAIA)
• Mcoin (M)
• MalibuCoin (MAL)
• Mammothcoin (MAMM)
• Mantiscoin (MNS)
• MastiffCoin (MAST)
• Metiscoin (MTS)
• MidasCoin (MID)
• MileyCyruscoin (MCC)
• MiracleCoin (MCL)
• Mjollnircoin (MNR)
• MMXIVcoin (MMXIV)
• Monocle (MON)
• Mozzshare (MLS)
• MtGoxCoin (GOX)
• Mugatucoin (MUGA)
• Muniti (MUN)
• Mycoin (MYC)
• N5coin (N5X)
• Nanite (XNAN)
• NewUniversalDollar (NUD)
• NewUniversalEurocoin (NUE)
• NewWorldOrdercoin (NWO)
• NFDcoin (NFD)
• NOAHcoin (NOAH)
• Noocoin (NOO)
• NopeCoin (NOPE)
• NTXcoin (NTX)
• Ocupycoin (OCUPY)
• OlympicCoin (OLY)
• Omega (OMA)
• OPEC Coin (OPC)
• OrthoCoin (ORTHO)
• Ottomancoin (OTC)
• ThePandacoin (PANDA)
• Pandacoin (PAND)
• Pawncoin (PAWN)
• PayCon (CON)
• Payprocoin (PRO)
• Payzorcoin (PZR)
• Pelecoin (PELE)
• PENCoin (PEN)
• Penguincoin (PENG)
• Pesacoin (PES)
• PetroDollar (XPD)
• PHCoin (PHC)
• Phenixcoin (PXC)
• Pimpcash (PIMP)
• Plankton (FOOD)
• Plutoniumcoin (RODS)
• Poolstamp (XSP)
• Potatocoin (SPUD)
• Preminecoin (PMC)
• ProfitCoin (PFC)
• ProtoShares (PTS)
• Prozcoin (PROZ)
• Pxlcoin (PXL)
• Pyramids (PYRA)
• QQCoin (QQC)
• QubitCoin (Q2C)
• Québecoin (QBC)
• QuidCoin (QUID)
• Rainbowcoin (LGBT)
• RapidCoin (RPD)
• Rawcoin (RAW)
• Rekt (REKT)
• Rescuecoin (RSCC)
• ReserveShare (RSU)
• RevoCoin (RVC)
• RhinoCoin (XRC)
• Riotcoin (RIOT)
• Rublecoin (RU)
• Sambacoin (SMB)
• Saturncoin (SAT)
• Savecoin (SPC)
• Scattercoin (STC)
• Securitysyscoin (SCSY)
• Seedcoin (SEED)
• Sharecoin (SHARE)
• ShinyCoin (SHC)
• ShopCoin (SHOP)
• ShopX (SHOPX)
• Siamesecoin (SIS)
• SiliconValleyCoin (XSV)
• Singularity (SING)
• Slimcoin (SLM)
• Snowballs (BALLS)
• SocialCoin (SOC)
• Spark (SPARK)
• Squarebit (SBIT)
• StakeCoin (STK)
• Stlcoin (STL)
• StopLosscoin (XSL)
• SummerCoin (SUM2)
• Suncoin (SUN)
• Takeicoin (TAK)
• Talkcoin (TAC)
• Teacoin (TEA)
• Techcoin (TECH)
• Theoremcoin (THEO)
• Tomatocoin (TMT)
• TraderCoin (TRDR)
• Twenty15 (2015)
• UCIcoin (UCI)
• UltimateCoin (ULT)
• Unattaniumcoin (UNAT)
• Universecoin (UNVC)
• UniversityCoin (UVC)
• UROdarkcoin (UROD)
• USBcoin (USB)
• Usecoin (USE)
• Vaultcoin (VAULT)
• Veilcoin (VEIL)
• VelocityCoin (VEL)
• VeniVidiVicicoin (VVV)
• Vexcoin (VEX)
• VikingCoin (VIK)
• VirtualCoin (VC)
• VolatilityCoin (VLT)
• VorteX (VTX)
• Voxpopulicoin (VOXP)
• Voyacoin (VOYA)
• WaccoinGold (WACG)
• Warofcoins (WOC)
• Wavecoin (WVS)
• WeAreSatoshi (WSX)
• Whistlecoin (WSTL)
• Wincoin (WIN)
• Wolfcoin (WLF)
• WTFcoin (WTF)
• X14coin (X14)
• XanonCoin (XAN)
• XCloudcoin (XCLD)
• DoubleEaglecoin (XDE)
• Xivra (XIV)
• Xurocoin (XURO)
• YangCoin (YANG)
• YellowCoin (YC)
• YinCoin (YIN)
• ZenithCoin (ZTC)
• Zipcoin (ZIPC)
• Zirkcoin (ZIRK)

Corrections welcomed.

Cheers

Graham