"It excludes the majority of housing costs faced by homeowners and differences in calculation mean it may be considered a better representation of the way consumers change their consumption patterns in response to price changes, " the 2010 Budget document explained.

BBC: Pension switch is 'unlawful', High Court hears

On the economy, the differences among candidates turn on whether a rise in the consumption tax is needed to plug a gaping budget deficit and bring down the high levels of debt incurred when Japan tried to spend its way out of slump in the 1990s.

ECONOMIST: Who will replace Junichiro Koizumi?