Diffusion of Innovations, explained.
The Bass diffusion model explores adoption driven by both external influence and imitation, producing patterns in new and cumulative adoption over time.
Why it happens
External influence can seed adoption before there are many existing users. Imitation grows with the adopted share, while the remaining pool shrinks as people join. The interaction can create a peak in new adoption followed by a plateau in cumulative adoption.
Adoption can come from independent discovery and from seeing others adopt.
Read the result
Distinguish new adopters per period from all adopters to date. Adjust external influence and imitation separately rather than assuming a steeper cumulative curve identifies which mechanism caused it.
A worked example
A new product reaches a market
Early customers adopt through direct exposure even when few peers use the product.
As users accumulate, imitation encourages further adoption. Eventually fewer potential first-time adopters remain.
New adoption can slow while cumulative adoption keeps rising. A declining flow is different from users leaving.
OPTIONAL DEEPER DETAILGo deeper: inside the model
Inside this model
The Bass toy update is ΔF=(p+qF)(1−F), where F is cumulative share, p=innovation/100 and q=imitation/100. Starting at zero, the chart runs 30 periods.
Where this idea is useful
A practical use
Explore how word of mouth changes the shape of a new product's rollout.
A common misconception
“Every S-shaped adoption curve proves imitation.”
Other processes can produce similar shapes. The Bass model is one explanation with explicit parameters, not proof of a mechanism from appearance alone.
What this explanation leaves out
- A fixed total market and constant coefficients are strong assumptions; the curve alone is not a sales forecast.
Is this the whole theory of diffusion of innovations?
No. Bass models a specific aggregate adoption process. Broader diffusion research also examines communication, social networks, attributes of innovations, and different adopter groups.
Are you tracking new adoption, the installed base, or continued use?
Associated thinkers
Further reading
Explore the original research or the teaching reference behind this experiment.