An attribution model decides how much credit each marketing channel gets when someone converts. If a user finds you through organic search, clicks a Facebook ad two days later, then converts via a direct visit, attribution tells you which channel deserves the win—or how to split it. The most common models are last-click (100% credit to the final touchpoint), first-click (all credit to discovery), linear (equal credit across all touches), time-decay (more credit to recent interactions), and position-based (40% to first and last, 20% split among middle touches). Google Analytics 4 defaults to data-driven attribution when enough conversion volume exists, using machine learning to weight channels based on actual impact. Why this matters: if you only look at last-click, you might kill your top-of-funnel blog content or brand campaigns because they rarely close deals directly—even though they start the journey. We've seen clients nearly pause profitable display campaigns because last-click attribution made them look worthless, when position-based showed they were driving 30–40% of assisted conversions. At Ottawa SEO, we typically start clients on data-driven attribution in GA4 if they have 400+ conversions per month across channels. Below that threshold, position-based is a safer manual choice because it acknowledges discovery and closing touches without needing algorithmic confidence. For e-commerce with short consideration cycles (under 7 days), last-click is often acceptable. For B2B or high-ticket services common in Ottawa—legal, SaaS, construction—multi-touch models are non-negotiable because sales cycles stretch weeks or months. One warning: attribution models don't account for offline conversions, phone calls triggered by digital ads, or brand searches that stemmed from a podcast mention. They work within tracked digital behaviour. If 20% of your leads call after Googling your brand name, last-click will credit "organic brand" when the real driver might have been a LinkedIn ad three weeks earlier. Cross-reference attribution reports with survey data or CRM notes to fill those gaps.