As the institutional use of open-source software continues to expand like an octopus, the public sector remains a key target market.

Government users like Linux and other open-source software for several reasons, but the most important ones are probably that total cost of ownership is often lower than it is for proprietary products and that open-source projects don’t vanish if the company providing them goes under.

Government IT folks are likely quite familiar with the perils of proprietary legacy systems - a recent Congressional hearing revealed that there are computers that date back to 1976 still in use at the federal level, and that critical taxpayer data is stored on a system written more than 50 years ago, in assembly language.

Worse, whole agencies still use computers running Windows XP, and even Windows 3.1 - meaning that it's difficult or impossible to support and update those systems.

Because of this, it’s become increasingly common over the past decade or so to see laws being passed to either mandate the use of open-source software or, at the very least, encourage people in government who make procurement decisions to do so. Here’s a map of the status of open-source laws around the world, via the magic of Google Fusion Tables.

Broadly speaking, Europe and South America are the biggest hotspots for open-source use in government, with Bulgaria being an example earlier this year of a country requiring all software written for the government to be FOSS (free and open source software). East Asia and North America also have plenty of countries with laws on the books (See also: The US federal government now has an open source policy – but it doesn’t go far enough). These laws are harder to find in Africa and central Asia, however.

A word on methodology: We used various sources of information on open-source laws to create the map, because there isn’t really a comprehensive, up-to-date database on the subject. (At least, not that we could find.)

“Unfortunately, a database of laws mandating or suggesting the adoption of open source software is missing, and difficult to create and update,” notes Italo Vignoli, the press director at the Open Source Initiative.

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So our two main sources were a report published in 2010 by the CENATIC Foundation, a non-profit backed by the Spanish government, and a 2013 study prepared for the European Commission by Belgian IT consultancy Trasys.

Obviously, both are varying degrees of out-of-date, but the idea behind the map isn’t to be an authoritative source on this topic, but an overview, to give you a general sense of how far the idea of governmental open-source use has spread. And it’s a pretty sizeable extent, we think you’ll agree.

It also required a fair amount of interpretation on our part – while it might seem like the existence of a law around government open-source software is pretty much cut-and-dried, this ignores three things. First, lots and lots of countries have active proposals to enact open-source legislation, so it didn’t seem right to simply lump them into the “no” column. Second, there are also plenty of cities and regional governments at various stages of adopting their own local laws. Finally, laws have different force and effect in different places, they use different wording, and it can occasionally be tricky to neatly separate them into buckets labeled “encourages” or “mandates.”

So, in the final analysis, some of this is a judgment call – countries without national laws on the subject might get an “encourages” if multiple major cities or regional governments have reasonably complete open-source laws, to reflect the fact that awareness and use of open-source is robust there. Like we said, this isn’t meant to be strictly authoritative, and if you base some kind of argument or, god forbid, a business decision on whether this map says a country is open-source-friendly or not, you’re nuts. It’s an illustration. Enjoy.