Remodeling the Working-Kaldor curve: The roles of scarcity, time to maturity and time to harvest

To explain convenience yield accruing to commodity inventory holders, time to maturity (TTM) and TIME to harvest should interact with current scarcity. Using weekly data for corn, wheat and soyabeans (1986–2009), the interaction (multiplicative)model performs better than traditional versions that, at best, incorporate TTM additively and ignore harvests. Among the competing proxies for scarcity, the combination of spot price and inventory beats either spot price or inventory separately, but the pure spot-price version is a close second. Our model still exhibits a clear ‘Working curve’ pattern, with slopes changing with TTM and pre- versus post-harvest periods.status: publishe