While it is common for a federation to be brought into being by agreement between a number of formally independent states, in a unitary state self-governing regions are often created through a process of devolution, where a formerly centralised state agrees to grant autonomy to a region that was previously entirely subordinate.
Mentres que unha federación adoita xurdir por acordo de estados formalmente independentes, nun estado unitario as rexións de autogoberno acostúmanse crear mediante procesos de descentralización, onde un estado previamente centralista concede autonomía a rexións que anteriormente foran totalmente subordinadas.