  The evolution of economic and innovation systems at the national scale is
shaped by a complex dynamics, the footprint of which is the nested structure of
the activities in which different countries are competitive. Nestedness is a
persistent feature across multiple kinds (layers) of activities related to the
production of knowledge and goods: scientific research, technological
innovation, industrial production and trade. We observe that in the layers of
innovation and trade the competitiveness of countries correlates unambiguously
with their diversification, while the science layer displays some peculiar
feature. The evolution of scientific domains leads to an increasingly modular
structure, in which the most developed nations become less competitive in the
less advanced scientific domains, where they are replaced by the emerging
countries. This observation is in line with a capability-based view of the
evolution of economic systems, but with a slight twist. Indeed, while the
accumulation of specific know-how and skills is a fundamental step towards
development, resource constraints force countries to acquire competitiveness in
the more complex research fields at the price of losing ground in more basic,
albeit less visible (or more crowded), fields. This tendency towards a
relatively specialized basket of capabilities leads to a trade-off between the
need to diversify in order to evolve and the need to allocate resources
efficiently. Collaborative patterns among developed nations reduce the
necessity to be competitive in the less sophisticated fields, freeing resources
for the more complex domains.
