You can estimate the popularity of an operating system in a particular region using indirect data - ascertaining the level of interest in an operating system. And you can find out the level of interest if you figure out the number of queries to search engines about a particular operating system. Fortunately, Google provides this kind of information, which the 
Pingdom guys used to assess the 
popularity of Linux in the world . I came across this idea - an assessment of the popularity of different operating systems - the other day, when I did the translation of the article " 
Linux popularity across the globe " and studied the 
popularity of BSD systems .
Windows

The top five countries by degree of interest in 
Windows (the full list can be found 
here ):
- India
 - Sri Lanka
 - Cuba
 - Russia
 - Pakistan
 
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Linux

The top five countries in terms of interest in 
Linux (the full list can be found 
here ):
- India
 - Cuba
 - Russia
 - Czech
 - Indonesia and Bangladesh
 
BSD

The top five countries in terms of 
BSD interest (the full list can be found 
here ):
- Indonesia
 - Russia
 - Moldova
 - Estonia
 - Czech
 
Solaris

The top five countries in terms of interest in 
Solaris (the full list can be found 
here ):
- India
 - Singapore
 - Japan
 - Sri Lanka
 - Bangladesh
 
Netware

The top five countries in terms of interest in 
NetWare (see the full list 
here ):
- Belarus
 - Russia
 - South Africa
 - Indrnesia
 - Jamaica and India
 
QNX

The top five countries in terms of interest in 
QNX (see the full list 
here ):
- Russia
 - Ukraine
 - Belarus
 - South Korea
 - India
 
ReactOS

The top five countries by degree of interest in 
ReactOS (the full list can be found 
here ):
- Russia
 - Indonesia
 - Estonia
 - Czech
 - Ukraine
 
UNIX

The top five countries by degree of interest in 
UNIX (the full list can be found 
here ):
- India
 - Singapore
 - Japan
 - Hong Kong
 - Kenya
 
AmigaOS

The top five countries by degree of interest in 
AmigaOS (the full list can be found 
here ):
- Norway
 - Sweden
 - Poland
 - Finland
 - Italy
 
Plan 9

The first five countries in terms of interest in 
Plan 9 (the full list can be found 
here ):
- Russia
 - Ukraine
 - Czech
 - Japan
 - Sweden
 
Minix

The top five countries by degree of interest in 
Minix (the full list can be found 
here ):
- Greece
 - Costa Rica
 - Russia
 - India
 - Indonesia
 
MULTICS

First five countries according to the degree of interest in 
MULTICS (the full list can be found 
here ):
- Mexico
 - India
 - USA
 - Brazil
 - Japan
 
Aix

The top five countries in terms of interest in 
AIX (the full list can be found 
here ):
- France
 - India
 - South Korea
 - Senegal
 - Hong Kong
 
HP-UX

The top five countries in terms of interest in 
HP-UX (the full list can be found 
here ):
- South Korea
 - Singapore
 - India
 - Kazakhstan
 - Japan
 
IRIX

The top five countries in terms of interest in 
IRIX (the full list can be found 
here ):
- Czech
 - India
 - South Korea
 - Greece
 - Norway
 
Mac os x

The top five countries by degree of interest in 
Mac OS X (the full list can be found 
here ):
- Switzerland
 - USA
 - Russia
 - Canada
 - Australia
 
System v

The top five countries in terms of interest in 
System V (the full list can be found 
here ):
- Slovakia
 - Czech
 - India
 - Pakistan
 - Slovenia
 
Tru64

The top five countries in terms of interest in 
Tru64 (the full list can be found 
here ):
- South Korea
 - Singapore
 - India
 - Switzerland
 - South Africa
 
OS / 2

The top five countries by degree of interest in 
OS / 2 (the full list can be found 
here ):
- Belarus
 - Russia
 - Dominicana
 - Ecuador
 - Ukraine
 
OpenVMS

The top five countries in terms of interest in 
OpenVMS (the full list can be found 
here ):
- Singapore
 - Czech
 - India
 - Slovenia
 - Sweden