Losing a tailwind

WHEN supply falls and demand is strong, prices tend to go up. So it has been in America’s stockmarkets. Short-term interest rates at record lows and minuscule yields on government bonds have boosted investors’ demand for equities. And thanks to share buy-backs, the supply of shares has been steadily falling. BCA Research estimates that the number of shares in issue on American stockmarkets has fallen by 6% since 2009. This tailwind for share prices, however, may be starting to fade.