[alephnil]

What is described in job announcements and what the job actually consists of can often be quite different though. Job announcements are a combination of what the management think or wish will be needed in the future and what they think will attract applicants. This means that technologies that are perceived as trendy will appear more often than those actually used, especially if the latter is perceived as legacy tech. The result is that job announcements may not be such a good indicator of what actually is used out there.

There is also a tendency that jobs that require deep understanding of some area (say video encoding, cryptography, statistics) not are announced, but instead the programming languages and the frameworks used in the surrounding system is announced as essential for the job. This means that if your core competency is in such areas, it can be hard to find the employers that need such skills, even if the skill is in demand.