As it lays the groundwork for raising interest rates, the Federal Reserve has been squeezing the annual growth rate of the real (inflation-adjusted) supply of so-called high-powered money (aka base money (M0)). But economic growth has turned wobbly lately, including yesterday’s disappointing report on industrial production for March. The slowdown bias overall is expected to pare US GDP growth in this year’s first quarter to a virtual standstill, according to the Atlanta Fed’s current projection. Given the current climate, it’s no surprise to learn that the year-over-year change for the real monetary base ticked higher in March after decelerating sharply for more than a year.

Is the mild revival in real M0 growth a clue that the Fed is having second thoughts on the timing of rolling out the first rate hike? Earlier this year the crowd was expecting the Fed to act as early as June. Analysts have pushed that out to September in recent weeks, although the latest macro releases suggest that the first hike may come even later.

But if we’re in delay mode again, St. Louis Fed President James Bullard didn’t get the memo. Yesterday he made the case for hiking rates sooner rather than later, although he was “deliberately vague” on his preference for a start date. John Williams, president of the Federal Reserve Bank of San Francisco, is a bit firmer in publicly sharing his thoughts on what should happen. In an interview published today with The New York Times, he says that “I do believe that we should be initiating rate increases later this year.”

Meanwhile, real M0 appears to be making a U-turn in the preliminary data for March. The St. Louis Adjusted Monetary Base (deflated by the consumer price index) ticked up to +4.2% last month vs. the year-earlier level. The mild bounce comes after an incremental decline in February, the first instance of red ink since late-2012.

Let’s not make too much of the change. In the grand scheme of the last several years, real M0 is still a long way from the 30%-plus increases in late-2013 and early 2014, when monetary stimulus was in high gear. It’s fair to say that M0’s direction is more or less neutral relative to recent history. Perhaps that’s appropriate in the wake of the mixed economic reports that leave the outlook a bit fuzzier than usual these days.

Whatever happens next, real M0 deserves close monitoring. The historical record for this measure of money supply has a close relationship with the business cycle, which is why it’s one of several key indicators in the monthly updates of CapitalSpectator.com’s Economic Profile. What’s the message at the moment? Liquidity growth has slowed to a crawl vs. the growth rates in recent years. That’s old news. The big mystery now is whether the latest bounce is a sign of things to come—or just a brief time out on the road to the first rate hike?