South Korea's stock market has delivered strong performance this year, but the rally appears to be driven by a narrow group of companies rather than broad-based gains across the market.

Meanwhile, global fund managers significantly increased their equity allocations during May, according to a Bank of America survey. The increase represents the largest monthly boost to equity positions recorded in the survey's history.

The concentration of Korea's market gains in a handful of stocks raises questions about the sustainability of the rally and whether the positive momentum can spread to a broader range of companies. Market concentration can create vulnerability if the leading stocks experience declines.

The Bank of America survey data suggests institutional investors globally are becoming more optimistic about equity markets, with fund managers moving capital from other asset classes into stocks at an unprecedented pace in May.

Both developments highlight the current dynamics in global equity markets, where strong performance in certain regions and sectors is occurring alongside increased institutional appetite for stock investments. The survey results indicate a shift in sentiment among professional investors toward greater risk-taking in equity markets.