Innovation policies also need to be consistent over time by using a portfolio approach with a long-term perspective. Driven by this insight, applied economic research on external effects, externalities or social costs have frequently taken the electricity sector as a starting point. In the 1990s and early 2000s, a series of broad, well-funded studies with dozens of high-level experts from different fields took on the full costs of electricity. Many of the results produced from these studies remain relevant today. While estimates of social costs inevitably display large uncertainties, the studies converged in the identification of key problem areas. However, decision makers never properly implemented the policy conclusions from these studies.