Most people worry about privacy. Yet, many would trade it for free pizza

More than 80 per cent said they want more control and choice over the collection and use of their personal information.

More than 70 per cent say that privacy is either extremely important or very important when choosing which good or service to buy.

The message from these surveys is crystal clear: people value their privacy a lot.

There's just one problem: their actions suggest the opposite.

Suppose I asked you to hand over your email address and the email addresses of your friends. Would you do it?

The above survey results suggest the answer is no. But the research suggests otherwise.

Susan Athey - a senior fellow the Stanford Institute for Economic Policy Research - ran this very experiment.

The obvious thing to do if your asked for email addresses and you want to protect your privacy and the privacy of your friends is simple: put down fake email addresses.

But the experiment had a catch. Half of the participants were offered free pizza in exchange for the email addresses while the other half got nothing.

Did the pizza make a difference? Turns out, it did. The researchers checked whether the emails were real or fake. The probability of getting fake email addresses was cut in half for students who received the free pizza.

For all our talk of wanting to protect privacy, the value we actually put on it is nothing more than few slices of pizza.

This experiment isn't a one-off.

One study found that the overwhelming majority of online shoppers were willing to give away their personal data for the mere chance of winning $100.

Another study found that, among survey participants who ranked themselves as being "very sensitive to privacy issues", less than half were willing to pay a mere $29 to have their privacy protected. Another study found that people were only willing to pay a few cents to avoid those annoying phone calls from telemarketers.

We can see this in our daily lives, too.

You could protect your privacy by using cash instead of credit cards and digital wallets, but we choose the former because it's slightly more convenient.

You could stop using TikTok, Facebook and Instagram to protect your privacy, but we do it anyway because it's a convenient way to stay in touch and be entertained.

In each instance, we are showing how little we value our own privacy.

You might say: what we want is to use these things without giving up our privacy. Sure. But this misses the point. The question is: how much do you value your privacy? And the research suggests that, more often than not, the answer is: very little.

The difference between what people say and what people do is not a new concept. It's what economists call stated preferences (what you say) versus revealed preferences (what you do). It's the reason why economists are suspicious of survey data.

It's not unique to privacy. If you asked every Australian how much alcohol and pornography they consume each week and added up all their answers, the sum would be nowhere near what statistics show to be the truth.

This isn't to say that privacy isn't important. There are plenty of instances in which we would be outraged if specific pieces of information or data were given away.

This underscores the core challenge of privacy: what constitutes "private information" varies widely between people, between circumstances and over time.

Who did you have dinner with last night? If it was your long-term partner, it's probably not private information. If you're single and you were on a date with someone new, then maybe it is private information.

If you're not single and were on a date with someone new, then it's definitely private information.

Most young people probably wouldn't care if their medical history got leaked for one simple reason: they don't have any medical history. But for older people, and people who do have medical conditions, that information could well be very sensitive.

The research shows this, too. One study found that people were happy to have data on their body weight shared, but only if their body weight was in line with what they considered to be normal.

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Another study found that, across Europe, the extent to which people were happy to have their mobile phone location data shared with others varied dramatically: some cared a lot, others not at all. It was impossible to predict how people would react.

Another study found that survey participants were more accepting of an organisation sharing their information when the economic benefits of doing so were explained to them.

And this is the crux of the challenge when it comes to privacy: there are clear, measurable economic benefits from collecting, sharing and selling data. The benefits of protecting privacy, on the other hand, are much less certain.

Make no mistake: the benefits of protecting privacy are real. But they depend on the individual, the circumstance and the specific point in time.

In weighing up these competing interests, the advice for policymakers is simple: don't listen to what people say, look at what they do.