APEC has 21 member economies, and none has joined since 1998
Asia-Pacific Economic Cooperation, or APEC, is a regional forum for trade and economic cooperation. It has 21 members, which it calls economies rather than countries because it deals with them as economic entities. Twelve took part from 1989. Nine more joined in three steps: 1991, 1993 and 1994, and 1998. None has joined since 1998. Observers attend meetings but are not members, so they are not on the list.
Name them all first. Then try the harder part: name the economies in each joining group.