Polyphony Digital, the studio responsible for the Gran Turismo franchise, have announced sales figures for each instalment in the long running series that saw its debut on the original Playstation in 1997.
The numbers are current up to September of this year, so it's reasonable to assume they have rounded 68 million in total.
Gran Turismo: 10,850,000
Gran Turismo 2: 9,370,000
Gran Turismo 3 A-spec: 14,890,000
Gran Turismo Concept Series: 1,560,000
Gran Turismo 4 Prologue: 1,400,000
Gran Turismo 4: 11,600,000
Gran Turismo 5 Prologue: 5,350,000
Gran Turismo PSP: 3,860,000
Gran Turismo 5: 9,010,000
Total: 67,890,000
Gran Turismo 6 has been confirmed to be in development, but at this point we can be sure it makes it out during on Playstation 3.