TOKYO -- Japan's public pension fund, one of the largest institutional investors in the world, has stirred a international debate with its decision to stop lending shares for negative bets on stocks. The Government Pension Investment Fund, which had 161 trillion yen ($1.48 trillion) in assets under management as of September, said last Tuesday that share lending risks "creating a de facto vacuum in the fund's holdings." The fund expressed concern that this practice "lacks consistency with our stewardship responsibility."