Since oil demand is seasonal, it is normally most helpful to compare demand with the corresponding time period of the previous year. This convention is always adopted unless specifically stated otherwise. Oil production, by contrast, is not generally seasonal (with the exception of seasonality resulting from the concentration of outages for maintenance in the summer in a few locations such as the North Sea). In general, the report focuses on changes in production compared with the last month or quarter, such as new fields coming onstream or production recovery from an unexpected outage. For this reason, in the Supply section of the report, changes in production are normally quoted in relation to the previous month or quarter as appropriate, except where specifically stated. Finally, product stocks normally follow a contraseasonal pattern to product demand and, as in the case of demand, absolute inventory levels are normally compared to those at the same time of year in previous years. However, as the balancing factor in supply and demand, month-on-month changes are also important. Thus, the best way to explain monthly stock developments is to discuss changes in demand, production, imports and exports compared to the previous month.

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