At the professional level, meetings began to offer significant financial incentives for all athletes in the 1990s in Europe with the creation of the "Golden Four" competition, comprising meetings in Zürich, Brussels, Berlin and Oslo. This expanded and received IAAF backing as the IAAF Golden League in 1998, which was later supplemented by the branding of selected meetings worldwide as the IAAF World Athletics Tour. In 2010, the Golden League idea was expanded globally as the Diamond League series and this now forms the top tier of professional one-day track and field meetings.