A group of investors led by prominent activist shareholder Yoshiaki Murakami said a push by the Tokyo Stock Exchange for better capital efficiency will strengthen their crusade to reduce Japan's unusually high number of chronically undervalued stocks.

Japan is almost unique among major economies in the number of companies whose shares are worth less than their assets — almost half of those listed on the Topix 500 index of big companies, compared with about 3% for the S&P 500 in the United States.

To address the matter, the exchange made a rare call a month ago for firms to disclose plans to improve capital efficiency, especially if their shares are trading below book value, triggering a wave of share buy-backs and dividend hikes.