Japan on course to choose woman prime minister in landmark first

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

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

But why does Japan keep changing leaders? This is partly because of it being a "one-party democracy", explains Professor James Brown of Temple University Japan.

The LDP's grip on the political landscape means the primary rivalry comes from within the party, rather than from external parties.

"So within the LDP there are intense conflicts within different factions - they all want their own faction to get the leadership position."

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

Main Reasons Behind Rapid Turnover

• Single-party rule limits outside challenges
• Internal factional rivalries drive leadership contests
• The prime minister's position is often described as a "poisoned chalice"
• Political stability stays elusive despite economic strength