IThe Federal Reserve’s pace of interest-rate hikes the next few years will be far more volatile than in previous cycles in part because of unpredictable shocks, with the central bank sometimes lowering rates, the Fed’s vice chairman said at the Economic Club of New York.

“A smooth path upward in the federal funds rate will almost certainly not be realized, because, inevitably, the economy will encounter shocks — shocks like the unexpected decline in the price of oil, or geopolitical developments that may have major budgetary and confidence implications, or a burst of greater productivity growth, as the Fed dealt with in the mid-1990s, ”

Citing the 2004 to 2007 rate increase cycle, when the Fed raised its benchmark rate at nearly every meeting, Fischer said, “I know of no plans for the (Fed’s policymaking committee) to behave that way.”

The Fed last week dropped an assurance to be “patient” as it considers its first rate increase since 2006, opening the door to a hike from the near zero rate as soon as June. But with inflation and wage growth stubbornly weak, Fed officials’ interest-rate forecasts indicate an initial increase is more likely in September.

Fischer reaffirmed that liftoff “likely will be wanted before the end of the year.”

Fed policymakers’ projections showed the pace of rate increases is likely to be unusually slow, with the fed funds rate rising to just 0.625% at the end of this year and 1.875% by the end of 2016.

But Fischer said the path of increases will be unpredictable. “There is considerable uncertainty about the level of future interest rates,” he said. “As monetary policy is normalized, interest rates will sometimes have to be increased, and sometimes decreased.”

The only certainty, he added, is that future rate increases will be based on the Fed’s goals of maximizing employment and keeping prices stable, and on economic data.