The separate streams of problems, policies, and politics come together at certain
critical times. Solutions become joined to problems, and both of them are
joined to favorable political forces. This coupling is most likely when a policy
window-an opportunity to push pet proposals or one's conceptions of problems-
is open.
Policy windows are opened either by the appearance of compelling problems
or by happenings in the political stream. Hence, there are "problems windows"
and "political windows." To return to our distinction between the agenda and
the alternatives, the governmental agenda is set in the problems or political
streams, and the alternatives are generated in the policy stream.
One key coupling is that of a policy alternative to something else. Entrepreneurs
who advocate their pet alternatives are responsible for this coupling.
They keep their proposal ready, waiting for one of two things: a problem that