Federal Reserve chairs speak cautiously in public, lest they incite severe economic consequences. Janet Yellen has maintained that responsible tradition in her nearly seven months at the helm of the nation's central bank.

So experts in the subtle language of Fed heads carefully analyzed her words in - and between the lines of - remarks she delivered last Friday at a Federal Reserve symposium in Jackson Hole, Wyo.

A telling sample from that speech: "Real wages have been rising less rapidly than productivity, implying that real unit labor costs have been declining, a pattern suggesting that there is scope for nominal wages to accelerate from their recent pace without creating meaningful inflationary pressure."

In other words, despite recent inflation warnings from some fellow Fed officials, and despite grocery-store sticker shock, the long-term policy of keeping interest rates very low will continue.

But though Chairwoman Yellen isn't deviating now from the course followed by predecessor Ben Bernanke, she conceded Friday that the Fed's "understanding of labor market developments and their potential implications for inflation will remain far from perfect."

In other words, the first woman to lead the Fed says she is taking the inflation threat seriously - just not seriously enough to retreat from the easy-money strategy of historically low interest rates.

Yet.

And she made herself clear, by Fed-speak standards, with this statement of the frustratingly obvious: "The economy has made considerable progress in recovering from the largest and most sustained loss of employment in the United States since the Great Depression. These developments are encouraging, but it speaks to the depth of the damage that, five years after the end of the recession, the labor market has yet to fully recover."

So when, if ever, will the Fed deem the recovery strong enough to require the anti-inflation defense of boosting interest rates?

Yes, the federal Consumer Price Index still reflects generally stable prices. But the CPI doesn't factor in food and energy prices. And food costs have been steeply climbing.

At least gasoline prices are down.

But for how long?

And how long can our record national debt, now more than $17.5 trillion, keep rising before it inflicts serious damage on the value of a dollar?

The stock market has performed remarkably well over the last two years. However, such "asset inflation" (equity prices rising at a much higher rate than other economic activity) has some analysts wary that another financial "bubble" is blowing up toward bursting.

Another unsettling modern trend: the investment community's perverse habit of rooting for weak job numbers to keep interest rates low.

How can high unemployment be a reassuring sign of long-term economic strength?

And how can Chairwoman Yellen, or anybody else, persuade Americans already paying painfully higher food prices that they need not fear inflation?