Korea's growth fund sells out in 4 days. Here's why markets care

South Korea's National Growth Fund is drawing attention from two corners of the market: retail investors rushing into a new state-backed product and equity investors tracking where the government's bigger policy money is going.

The retail-facing product almost sold out in four selling days, with 99.9 percent of its 600 billion won ($400 million) allocation taken up as of Thursday, according to the Financial Services Commission.

But the retail frenzy is only the most visible piece of a much large ...