Improving economic conditions
Recent data have boosted hopes that the euro zone's recovery is taking hold, with gross domestic product beating expectations to grow by 0.3 percent in the fourth quarter of 2013.
Unemployment figures released Wednesday added to this positive sentiment, with data showing that unemployment fell by 35,000 in February.
"Macro data released since the last ECB meeting in March has shown that the recovery is not only on track but is also more robust than previously thought," Carsten Brzeski, senior economist at ING, said in a note. "In short, the economy is doing exactly what the ECB had expected."
Draghi has said the ECB needs more information on the recovery before intervening, and signs of improvement could relieve some pressure to act.
Another theory is that the ECB never planned to ease policy at all. Instead, the ECB could be hoping that carefully-planned communication is enough to control conditions in the euro zone -- something Brzeski describes as "talking the talk in order not to have to walk the walk."
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"This plan would be to make extensive use of aggressive communication only, hoping for the dollar to strengthen and for euro zone inflation to pick up finally from April onwards," Frederik Ducrozet, senior euro zone economist at Crédit Agricole, said in a note.
Stand by for the bazooka
Alternatively, the ECB could be holding fire in anticipation of using its "bazooka". Draghi has repeatedly said there are multiple policy tools at the ECB's disposal, and some of the more unconventional measures have recently garnered attention.
Last week, Germany's Bundesbank President Weidmann stoked interest by telling newswire MNI that bond-buying, or quantitative-easing (QE), had not been ruled out.
Such a measure would be a drastic change in policy. Indeed, the move could be so drastic that the ECB could be storing it up for a crisis point.
"We've been pushing the idea that they should - and may well - do it (QE)," Loynes told CNBC, adding: "We would actually prefer QE because it's the only powerful tool left in the ECB's locker."
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