Google’s holding its annual conference for marketers today in San Francisco, and to kick it off they’re announcing some new tools advertisers can use. One of them promises to tie your offline credit card data together with all your online viewing to tell advertisers exactly what’s working as they try to target you and your wallet.

Attribution is important to businesses, because marketing costs money. Businesses are willing to spend some money on advertising and outreach — but only if they see it translate into a return.

That return, for decades, was hard to measure in all but the most vaguely correlative of ways. Did people buy your product after seeing your TV ad? After seeing your billboard? On a whim after seeing neither? Who knows!

But in the age of highly targeted, algorithmic advertising, the landscape is completely different. The apps on your phone know what you looked at and when, and can tie that in to what you see on other devices you’re also logged into their services on (like your work computer).

Meanwhile, you’re leaving tracks out in the physical world — not only the location history of your phone, but also the trail of payments you leave behind you if you pay with a credit card, debit card, or app (as millions of us do).

Put A and B together, and suddenly you have a much clearer picture to share with advertisers: Why yes, John Smith did see four ads for your coffee drink online yesterday, before spending exactly what one of those drinks costs at a location of yours near his office. Congratulations, your ads work; spend more money advertising with us now, please.

Coordinating all those different online and offline data points into one single person’s profile has basically been the holy grail of advertising for years now. Facebook, the world’s second-biggest advertising company (Google’s largest, and everyone else is a distant third), got there first when it launched Facebook Atlas in 2014. That service let Facebook generate universal cross-platform profiles: Any activity on any device you’ve logged into Facebook on counts as “you,” and can be collated into one profile for measuring advertising efficacy.

Google also introduced some offline measurements to its online tool suite back in 2014, when it started using phone location data to try to match store visit location data to digital ad views. But a store doesn’t make any money when you simply walk into it; you need to buy something. So Google’s tracking that very granularly now, too.

“In the coming months, we’ll be rolling out store sales measurement at the device and campaign levels. This will allow you to measure in-store revenue in addition to the store visits delivered by your Search and Shopping ads,” Google explains to advertisers. That’s very literally a collection of spending data matched to the people who spent it, matched in turn to people who saw ads.

Businesses that collect your email address to track your purchases and send you coupons can import their loyalty program data directly into their Google advertiser account, making it even easier to follow you around everywhere you go. For everyone else, Google says its third-party partnerships capture roughly 70% of all credit and debit card transactions in the U.S.

The data won’t have your name attached, Google makes sure to point out. It’s anonymized and then hashed over, so what advertisers see is that user 08a862b091c379fe9767615d10873 saw these ten ads in the morning, and spent $27.73 at a certain grocery store that afternoon.

That said, “anonymity” is pretty much anything but.If anyone’s looking at your digital breadcrumbs, they can be reasonably sure you are you from shockingly little data. Studies have shown that it it only takes three pieces of data to identify you by credit card spending alone, or two to identify you from a social media app.

On top of that, the larger picture of big data is, frankly, kind of overwhelming. FTC research has found that has found that cross-device tracking is everywhere and poorly disclosed. And finely granular ad targeting can have real harms, from small scale price discrimination to unintentional racial discrimination or even completely illegal racial discrimination that perpetuates housing segregation.

You have a little more control over how Google uses your data (for now) than over Facebook does, at least. You can visit Google’s advertising and privacy settings to opt out of having some of your activity logged, and to opt out of being shown some ads. But your history of ad viewing is still going to be out there, tied to your credit card spending, without a whole lot you can actually do about it.

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