The development of solar photovoltaic technology is one example of a positive tipping point dynamic. The introduction of the German Renewable Energy Act (EEG) – a modest national policy intervention – established a market for renewable power in Germany. This led to an expansion of renewable energy generation, triggering strong learning effects and falling costs that made renewable energies attractive in other countries. Renewables then entered a virtuous cycle of self-reinforcing market growth and global cost improvements.