Leaders are Hard to Beat: Coke Zero vs. Pepsi Max

Coke Zero was launched in 2006 with the ambition of being as big as Diet Coke in 10 years. I posted back in 2006 asking questions about the rationale for Coke Zero and how successful it would be. Well, 4 years into that 10 year journey, and the status is (mkt share 4 weeks to 26 Dec 09): Coke Zero: 2.2% share, lowest share since launch Diet Coke: 26.8% share, +1%pt So, why is Coke having such a hard time?