The Bank of Japan (BoJ) just raised some eyebrows in the financial world. Last Friday, the central bank announced it’s introducing “greater flexibility” into its monetary policy, notably loosening its yield curve control (YCC). This unexpected twist left global markets and investors a little rattled, leading to fluctuations in the yen against the dollar, while Japanese stocks and government bonds took a hit.

The BoJ’s decision also had a domino effect on other global markets. Europe’s Stoxx 600 opened lower while government bond yields in the region hopped. Even the S&P 500 and the Nasdaq felt the tremors, closing lower on Thursday ahead of the BoJ’s statement.

“Nobody saw this curveball coming,” Shigeto Nagai, head of Japan Economics at Oxford Economics, commented on the surprising turn of events.

So, why the big fuss over the BoJ’s policy tweak?

For years, the BoJ has followed a dovish stance, diligently adhering to strict yield curve control. This policy involves the central bank targeting a specific interest rate and then buying or selling bonds to meet that target. The aim is to stimulate Japan’s economy, which has wrestled with disinflation for a considerable period.

In its recent policy statement, the BoJ communicated it would permit 10-year Japanese government bond yields to fluctuate within the range of 0.5 percentage point on either side of its 0% target. However, it’s also opening the door to purchasing 10-year JGBs at 1% through fixed-rate operations, effectively broadening its tolerance by an additional 50 basis points.

This decision has left economists and investors scratching their heads: is this a minor technical adjustment, or does it signal the beginning of a more profound tightening cycle?

Tightening monetary policy, which involves central banks raising interest rates, is usually a response to high inflation. Both the U.S. Federal Reserve and the European Central Bank have adopted such a strategy over the past year.

Although the BoJ didn’t directly mention combating inflation as the reason for the policy change, it did acknowledge stubbornly high inflationary pressure by revising its forecast. The BoJ now expects core consumer inflation, excluding fresh food, to hit 2.5% in the fiscal year to March, an increase from a previous estimate of 1.8%.

Despite the chatter about the bank’s possible shift from dovish to neutral, BoJ Governor Kazuo Ueda has downplayed the significance of the policy tweak. In a news conference following the announcement, he insisted that this move aims to improve the sustainability of their policy rather than indicating a change in policy direction.

As we move forward, all eyes will be on inflation figures. “If inflation continues to overshoot the target, there’s a higher chance that the BoJ will follow this yield curve control adjustment with a significant tightening of monetary policy,” economists at Capital Economics commented.

However, it’s not just about the ‘if’ – timing is everything, according to Michael Metcalfe of State Street Global Markets. He noted that the yen, which is currently deeply undervalued, stands to benefit in the medium term if inflation has indeed returned to Japan and the BoJ finds itself needing to raise rates.

The BoJ’s latest maneuver has stirred up some doubts about the effectiveness of its yield curve control, with some experts arguing that it disrupts the natural functioning of the markets.

“As the BoJ gradually dismantles YCC, expect the yen to rally just as slowly,” Kit Juckes, a strategist at Societe Generale, said.

Whether this is the beginning of the end for the BoJ’s yield curve control, only time will tell. But one thing is for sure – this unexpected shift has given entrepreneurs, investors, and market-watchers around the world plenty to think about.