The nation on course to choose female prime minister in historic first

In the past twenty years, the country has had more than 10 leaders.

Actually, one expert likens taking up the nation's top job to drinking from a "poisoned chalice".

But why does Japan frequently replace leaders? This is partly because of it being a "single-party system", says Prof James Brown of Temple University Japan.

The LDP's grip on the country's politics means the primary rivalry comes from inside the party, instead of from external parties.

"So within the LDP there are vicious struggles within different factions - they all want their own faction to get the top job."

"Thus although you might be chosen as prime minister, as soon as you're in office, you have dozens of people manoeuvring to try to get you out again."

Main Reasons Behind Frequent Changes

• Single-party rule restricts external competition
• Party infighting fuel leadership contests
• The leadership role is frequently called a "poisoned chalice"
• Government continuity remains difficult to achieve despite financial power