Spanish is a Romance language, so one would expect it to be spoken mostly in countries where other Romance languages are spoken, and the map confirms this trend, although Spanish seems to be moderately popular also among speakers of Germanic languages.
The percentages are generally very low among speakers of other language families. This may be explained, at least in the case of Slavic and Baltic languages, by natural preference of speakers of those languages to learn languages more related to their own, such as Russian.
The map is based on the “Special Eurobarometer 386” and on the number of native Spanish speakers in the respective countries (the data is from 2012, so Croatia is not included).
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