Whenever there’s a shutdown of internet access or restrictions placed on an app, we shake our heads disapprovingly because we know it’s a fundamentally bad idea to do that. But what exactly is the cost of those shutdowns? A new study from the Brookings Institution suggests well over $2 billion over the last year.

The study, by Brookings analyst Darrell West, is a very rough estimate of these costs. We’re talking back-of-napkin rough — well, assuming you were sitting at the bar with MIT and World Bank economists.

Essentially, West collected numbers indicating how much of a country’s GDP can be reasonably estimated to be fully internet-based, or how much money in that country relied on a given app. Divide that by 365 and multiply by the number of days the shutdown occurred, carry the 7, and voila:

That’s just the top few countries — the list goes on quite a bit longer, as a good deal of countries shut down the internet or individual apps between July of 2015 and June of 2016. The total comes to about $2.4 billion.

West cautions that this number is just an estimate, and likely a very low one:

It is important to point out that this analysis only looked at the economic impact on Gross Domestic Product. It did not include estimates for lost tax revenues associated with blocked digital access, impact on worker productivity, barriers to business expansion connected with these shutdowns, or the loss of investor, consumer, and business confidence resulting from such disruptions. As such, the $2.4 billion figure is a conservative estimate that likely understates the actual economic damage.

Still, it’s a start: If a leader thinking of flipping the kill switch is informed that it’s going to cost the country a million dollars an hour and inhibit activity at all levels of business and governance, they might think twice — or at least turn it back on a little sooner than planned.