Adoption rates

Dion Hinchcliffe wrote in 2011: "I've been studying social software adoption patterns in the enterprise and early critical mass is often as little as 20% and stays there for some time".

My study of social software adoption rates is in the very early stage but it seems that on average the adoption rate during the first 6 months after implementation is closed to 30%. The question is what is the adoption rate? Traditionally, it is the number of organizational members who start using social software during a specific period of time. What will be this “specific period of time”? Let us compare two organizations which start using Jive. Both of them reached 30% engagement or usage but one organization has reached this number in 3 months and another in 6 months. Which organization has the highest rate of adoption? I would say the one that reach the highest percentage of engagement in shorter time period.