With the recent Facebook Cambridge Analytica scandal there’s been a lot of concern over, not just Facebook, but all tech companies and the massive amount of personal data they collect from their users. Most people don’t realize how much personal data they willingly relinquish to tech companies in exchange for their services. Nor do people realize just how valuable their personal data is.

We are in the age of big data. Data is the most valuable thing in the world. Whoever owns the most data in a given market will dominate that market. Everyone has access to all public data on the internet, so the real power or advantage in the marketplace comes from private data.

Facebook has a lot of private personal user data, which they sell to third parties, but Google has even more data—perhaps the most. Google has data on everything you type into Google search, every web page you visit on Chrome, every Gmail you send, every YouTube video you watch, every Google doc you write, every file you save in Drive, and so on. It’s the same for other tech companies like Facebook, Amazon, Apple, Dropbox, and more. They all gain their value from the personal user data they collect.

As the old adage goes, if you’re not paying for a product, you are the product. With all the personal data these companies collect, they know more and more about you—your tastes and preferences about everything from movies and food to politics. With enough data, they can know virtually everything about you—better than you even know yourself. Then they can use that data to sell products directly to you, or sell the data to other interested parties.

It’s become fashionable to hate on Facebook right now, but Google, Amazon, and Apple have just as much personal data. If you own an iPhone, Apple knows every text message and phone call you’ve ever made, plus every place you’ve ever been, with GPS precision. Amazon knows everything you’ve bought, or even thought about buying. Google knows everything…period.

The search engine is the most valuable algorithm because it’s the literal key to the internet. Without a search engine, you couldn’t find anything among the billions of web pages. Because Google is the most popular search engine, it has the most data and therefore power on the internet. The Amazon search engine is also massively popular. Every time you search for a product to buy, Amazon collects and saves that data. There are no regulations. Tech companies can do whatever they want with their data.

Today, it’s almost impossible to avoid using an internet service that doesn’t collect your data. Though just because a company collects your data, that doesn’t necessarily mean they are using it for nefarious purposes. But people need to be more aware of the power of data. The real question is do you trust Google (and Facebook, and Amazon, and Apple, and every other tech company collecting your data) to not be evil?