Consider how a “balanced portfolio” yielding “balanced returns” worked out for middle-class retirees in Venezuela.

The fantasy that a “balanced portfolio” yielding “balanced returns” will fund a stable retirement for decades to come is widely accepted as a sure thing: inflation will stay near-zero essentially forever, assets such as stocks and bonds will continue yielding hefty income and capital gains, and all the individual or fund needs to do is maintain a “balanced portfolio” of various asset classes that yield “balanced returns,” i.e. some safe “value” lower-yield returns and some higher risk “growth” returns.

This fantasy is based on the belief that yields will exceed real inflation for decades to come. That is if inflation is 2%, and the average yield of a “balanced portfolio” is 6%, then the inflation-adjusted return is 4% annually–not great, but enough to secure retirement income.

What few dare ask is: what happens if inflation is 7% and yields drop to 2%? Then the retirement fund loses 5% of its purchasing power every year. In a decade, the fund’s value will decline by roughly half.

Oops. Analysts such as John Hussman have been pointing out that historically, eras of outsized returns such as the past decade are followed by eras of low or even negative returns. So assuming a “balanced portfolio” of corporate and sovereign bonds, growth stocks, index funds, etc. will yield 6% to 7% like clockwork is essentially betting that this time is different: high growth will never pause or reverse.

But let’s say things really unravel, and inflation is 8% and yields are negative 2% for a few years. Retirement funds will lose 10% of their purchasing power every year. In a few years, the fund will lose half its value.

What happens if the current “everything” asset bubble pops, and inflation starts running away from policymakers? It’s worth recalling that declines on the order of 75% to 80% are common when bubbles finally pop–for example, the Nasdaq stock index post-2000.