Japan suffered its own debt-fuelled financial crisis in 1990, and ever since then the country has suffered from de-flation - falling prices.

BBC: Budget 2013: Radical options for the UK economy

The composite rate can never go below 0%, so even if we experience a prolonged period of severe de flation, the I Bonds will still help protect the future spending power of your investment.

FORBES: Inflation Is Back And So Are I Bonds