Integration in the English wheat market 1770-1820

Cointegration analysis has been used widely to quantify market integration through price arbitrage. We show that total price variability can be decomposed into: (i) magnitude of price shocks; (ii) correlation of price shocks; (iii) between-period arbitrage. All three measures depend upon data frequency, but between-period arbitrage is most affected. We measure variation of these components across time and space using English weekly wheat price data, 1770-1820. We show that conclusions about arbitrage are sensitive to the precise form of cointegration model used; different components behave differently; and different factors – in terms of transport and information – explain behaviour of different components. Previous analyses should be interpreted with caution.