  The global workforce is urged to constantly reskill, as technological change
favours particular new skills while making others redundant. But which skills
are a good investment for workers and firms? As skills are seldomly applied in
isolation, we propose that complementarity strongly determines a skill's
economic value. For 962 skills, we demonstrate that their value is strongly
determined by complementarity - that is, how many different skills, ideally of
high value, a competency can be combined with. We show that the value of a
skill is relative, as it depends on the skill background of the worker. For
most skills, their value is highest when used in combination with skills of a
different type. We put our model to the test with a set of skills related to
Artificial Intelligence (AI). We find that AI skills are particularly valuable
- increasing worker wages by 21% on average - because of their strong
complementarities and their rising demand in recent years. The model and
metrics of our work can inform the policy and practice of digital re-skilling
to reduce labour market mismatches. In cooperation with data and education
providers, researchers and policy makers should consider using this blueprint
to provide learners with personalised skill recommendations that complement
their existing capacities and fit their occupational background.
