Single-touch models
First touch credits the interaction that created the lead. It answers where demand originates and systematically undervalues everything that happens afterwards. Last touch credits the final interaction before the deal. It answers what closed the sale and systematically overvalues channels that capture intent someone else created, most obviously branded search and direct visits.
Multi-touch models
Linear divides credit equally across every recorded touch, which is simple and treats a passing web visit as equal to an hour-long meeting. Time decay weights later touches more heavily, on the assumption that recent contact carried more influence. Position-based, often U-shaped, assigns large fixed shares to the first and last touches and splits the rest among the middle. Data-driven models derive the weights statistically from patterns across many completed journeys, which is the most defensible approach and requires more volume than most businesses have.
A worked example on one deal (illustrative)
A deal worth ₹1,00,000 has four recorded touches in order: an organic article, a paid advertisement, a webinar, and a direct visit to the pricing page. First touch credits the article with the whole ₹1,00,000. Last touch credits the direct visit with the whole ₹1,00,000. Linear gives ₹25,000 to each of the four. Position-based at a forty, twenty, forty weighting gives ₹40,000 to the article, ₹40,000 to the direct visit, and ₹10,000 each to the advertisement and the webinar. Time decay might give roughly ₹10,000, ₹15,000, ₹30,000 and ₹45,000 across the four in sequence. Nothing about the deal changed. The apparent value of the paid advertisement moved between zero and ₹25,000 purely on the basis of a modelling choice, which is why running more than one view is more honest than defending a single one.