By Mary Williams Walsh, includes “The Pennsylvania teachers’ retirement fund put more than half its assets into risky alternative investments. The math didn’t work out, spurring an investigation. … Joseph M. Torsella … said he thought putting public money into private investments could be ‘dangerous,’ in part because the extent of the fees is poorly understood, and because the investments don’t trade on public markets and therefore have no listed market values. ‘Private valuations are very susceptible to manipulation,’ he said …”