The shape is a century old. The AIDA sequence, attention, interest, desire, action, is credited to the advertising writer E. St. Elmo Lewis around the turn of the twentieth century and was set out in print by E. K. Strong in 1925; the funnel drawing added the narrowing, since more people notice than consider and more consider than buy. Modern versions rename the stages (awareness, consideration, conversion, retention, advocacy) and add a bottom that widens again for repeat purchase and referral, which is the shape HubSpot formalised as the flywheel: attract, engage, delight, with happy customers feeding the next turn.
| Stage | The person | Channel and content | Measure |
|---|---|---|---|
| Awareness | Has a problem, has not named it | Search, social, display; explainers | Reach, new visitors |
| Interest | Knows the category, exploring | Content, email capture; guides, tools | Return visits, subscribers |
| Consideration | Comparing options | Comparisons, case studies, retargeting, demos | Enquiries, trials, basket adds |
| Purchase | Choosing and paying | Pricing page, checkout, sales call | Conversion rate, revenue |
| Retention and advocacy | Using it, telling others | Onboarding, support, newsletter, referral | Repeat rate, referrals, reviews |
The model earns its keep in three places. It assigns each channel a job and a measure, so that a content team is not judged on sales it cannot cause and a paid-search team is not judged on awareness it did not buy. It locates the leak: a business with plenty of traffic and few enquiries has a consideration problem, which is conversion rate optimisation work, while one with enquiries that never close has a sales problem no marketing can fix. And it sequences automation, since marketing automation is the funnel made executable: a subscriber who downloads a comparison moves a stage and receives the next message.
- Top of funnel is judged on reach and the cost of a new visitor; its content is educational and its budget is the easiest to cut and the slowest to rebuild.
- Middle of funnel is judged on whether people come back and identify themselves; it is where most businesses have no content at all.
- Bottom of funnel is judged on conversion and revenue; it is where the pricing page, the checkout and the sales process live, and where a small improvement is worth most.
What the model misses is the loop. Google's consumer research gave the middle its popular name, the messy middle, for the way buyers cycle between exploring and evaluating rather than descending a staircase; attribution reports show the same thing in the number of touches before a purchase. The practical response is to stop expecting a person to move in order and to make every stage's content reachable from every other, so that a reader who arrives at a comparison can find the explainer and a reader of the explainer can find the price. The marketing strategy and fundamentals courses teach the model; HubSpot's Inbound Marketing certification teaches the flywheel version with its stages and the content for each.