[Editorial] When rules bend

A rising market can flatter almost any investment strategy. South Korea’s recent selloff has revealed the cost of treating a public pension fund as an ally of a booming stock market.

Global doubts over AI spending and shifting expectations for US interest rates have helped drive the retreat. Those pressures do not explain why the National Pension Service entered the downturn with so little room to respond.

The NPS manages contributions meant to support retirement over decades. Its investment framework relies on rules that hold through changing market conditions. Rebalancing is central to that discipline. When equities rise beyond their target share, the fund sells some holdings; when prices fall, it can buy.

The NPS cannot eliminate losses, but disciplined allocation can limit concentration and preserve room to buy during downturns.

This year, the NPS loosened that discipline as Korean shares surged. In January, the NPS raised its domestic-stock allocation target from 14.4 percent to 14.9 percent and postponed rebalancing. In May, the target was lifted again to 20.8 percent, while the permitted range around it was widened.

The pause lasted through June. The fund retained more shares during the rally, leaving less flexibility when prices reversed.

The reported value of NPS stakes of at least 5 percent in 287 listed companies fell by about 182 trillion won ($137 billion) between June 30 and Thursday.

Samsung Electronics and SK hynix accounted for about 72 percent of that decline, exposing how heavily the portfolio depended on two chipmakers.

These were declines in market value, not realized losses on sales. Share prices may recover. Even so, their scale raises questions about why the NPS relaxed its allocation rules near the market peak.

NPS managers say a strict application of the previous rules would have required sales exceeding 800 billion won a day, potentially unsettling trading. That concern is legitimate.

Yet it also points to the purpose of predetermined allocation bands: Difficult choices should be governed by rules set in advance, rather than improvised once a correction is underway.

A pension fund cannot credibly promise discipline if guardrails are moved whenever they threaten to trigger selling.

The accelerated listing of leveraged exchange-traded funds linked to Samsung Electronics and SK hynix raises a separate question about financial oversight. Their listing process took 29 days, compared with a usual average of 62.

Separately, retail investors realized more than 2.3 trillion won in losses on single-stock leveraged and inverse exchange-traded products between May 27 and Aug. 14, according to figures submitted by the Financial Supervisory Service to lawmakers.

Leveraged products magnify market moves and warrant scrutiny. The fast-track process alone does not establish improper influence, but regulators should explain why the timetable was shortened and whether the review was adequate.

The pension fund’s own decisions are also difficult to assess because minutes of the committee meetings that approved the changes are not due for release until 2030.

Delayed disclosure can protect market-sensitive information. But the NPS should not leave the public waiting years to understand the reasoning behind a major change in long-term investment policy. It must explain the principles used, even if details of future trading plans remain confidential.

The government should shield the fund’s allocation decisions from short-term policy goals and require independent review of major changes.

Korea’s NPS is large enough to affect stock prices. Its credibility depends on resisting the urge to manage them. Market stability requires strict adherence to institutional discipline rather than policy expediency.

Markets may recover from the current decline. Confidence will be harder to restore if contributors come to believe that the rules governing their retirement savings shift with the fortunes of the index.