In every modern political system, power is shared to a greater or
lesser extent between levels of government. These power sharing
arrangements are perhaps most explicit in formal federal systems
like the United States and Canada, where federal constitutions
define the relative powers of central and subnational governments.
They may be no less important, however, in unitary democracies and
even authoritarian regimes where central governments require local
actors to implement policy on the ground and often delegate
significant authority to them. Indeed, in any large and complex
modern society, effective governance requires some sharing of power
between higher levels of government, capable of coordinating many
disparate actors and interests, and lower levels of government,
capable of responding to local conditions.