Estonia is governed under the constitution of 1992. The president, who is the head of state but has little substantive power, is elected by parliament for a five-year term and is eligible for a second term. The government is headed by the prime minister, who is nominated by the president and approved by parliament. The unicameral Parliament ( Riigikogu ) has 101 members who are popularly elected to serve four-year terms. Administratively the country is divided into 15 counties.