Google has held a majority of US search advertising dollars every single year since eMarketer started tracking the market in 2008. That ended in 2026.
eMarketer's latest forecast puts Google at 50.5% of total US search ad spending this year — and given that Amazon's search ad revenues are growing at 17.6% versus Google's 7.6%, the trajectory points one direction. The story most marketers expected was ChatGPT stealing queries or TikTok eating discovery. The actual threat to Google's search ad dominance is more boring and more consequential: Amazon.
Who took the share, and why
Retail media search ad revenues in the US are growing at 18.7% this year — nearly four times faster than the rest of search (5.0%). Amazon alone accounts for $23.95 billion of the total $29.69 billion US retail media search market. Walmart is a distant second.
This isn't surprising if you spend time in category-level data. Product purchase queries have been migrating to Amazon for years. "Best trail running shoes" might start on Google. "Brooks Ghost 16 women's size 8" increasingly starts on Amazon — because the inventory, reviews, and checkout are all in one place. Ad dollars follow queries.
The conversion loop problem
What makes Amazon's position structurally hard to dislodge: the conversion loop closes on the platform. When someone searches for a product on Amazon, adds it to cart, and checks out, that's a single-session conversion with no redirect, no landing page dependency, no site speed variable. For buyers, that frictionlessness becomes habit.
For you as an advertiser, the implication is that a portion of your high-intent product queries never land on Google at all. So if your Google ROAS on product-specific terms is trending softer while category demand looks healthy, Amazon may be capturing the easiest conversions upstream. If your attribution only covers Google and Meta, you can't see this — you just see conversion rates drifting down.
What the eMarketer summit said out loud
At their Ad Buyer Strategies Summit in New York this week, eMarketer framed this as a structural inflection point. The framing was blunt: Google's share dipping below 50% is not about the rise of AI search engines. It's the steady, compounding growth of retail media.
That distinction matters because a lot of brand-side teams are still waiting for the AI search picture to settle before rethinking search allocation. That's probably the wrong frame. The retail media shift already happened. AI search may accelerate it — AI Mode and ChatGPT product recommendations both default to surfacing shoppable results — but the ground has already shifted without it.
What this looks like in a real budget
Most e-commerce brands still treat Amazon search ads as an add-on to Google, not a parallel search channel. Budget planning typically starts with Google, fills Meta, then allocates whatever's left to Amazon. That sequencing made sense when Google held 60%+ of search ad spend. It makes less sense when Amazon owns 22% and growing.
A more accurate mental model: you have two search channels. Google handles informational, comparison, and brand-adjacent queries. Amazon handles purchase-ready, product-specific queries for physical goods. They serve different intent stages, carry different conversion windows, and require different measurement approaches. Running them off the same budget logic leads to systematic underinvestment in whichever channel has higher purchase intent for your category.
The practical check: add up your total paid search budget across both platforms. What share does Amazon represent? If it's under 15–20% and you sell physical products, the data suggests your allocation hasn't caught up with where buyers are searching.
What Google is doing about it
Google isn't passive here. Google Marketing Live on May 20 is expected to address expanded AI Mode placements, Direct Offers (discounts embedded into AI-generated responses), and agentic shopping capabilities. The goal is to make AI Mode feel like a shopping surface with purchase intent — not just an answer engine.
Whether that works depends on a behavior problem, not a product problem. Google can ship features faster than it can change where people go when they want to buy something specific. Amazon's advantage isn't the ad platform — it's that the transaction happens there, which means the data, the reviews, and the buyer habit all compound in Amazon's direction over time.
Google below 50% for the first time in nearly two decades is the signal that your search budget allocation needs a real update.
If you want to see how your current spend maps against where purchase intent is concentrating, the free Gromerce audit gives you a clear picture in a few minutes.
Related articles: google-pmax-vs-search-2025 · google-ads-ai-mode-placement-2026 · google-ads-ctr-rising-conversions-flat
Sources: eMarketer, EMARKETER Ad Buyer Strategies Summit New York, May 2026
