Over the last 25 years, capitalism has changed with capital becoming more globally mobile. Finance has transitioned from a helper to a driver of economic growth and accumulation, with speculative finance acting as a secondary engine of growth to make up for weaknesses in productive investment. This phenomenon of the increasing importance of financial markets, motives, institutions, and elites in both national and international economic operations and policy is referred to as "financialization". In the 1990s, financialization in the US led to closer ties between large industrial and financial firms, influencing the Federal Reserve under Alan Greenspan to emphasize appreciating financial assets in monetary policy goals.