A further distinction is the number of chambers in the national legislature; unicameral systems with one chamber or bicameral ones with a lower house and an upper house. Federations and countries with strong regional differences or regional identities are normally bicameral, to reflect the regions' interests in national bills. The states with the larger populations, from the Netherlands upwards, all have a bicameral system. Although there is a greater mix among the smaller states (some influenced by their federalist structure), the smallest states are on the whole unicameral.