Reporting environmental and social data differs from reporting financial data in a number of important ways. There are inherent limitations to the accuracy, precision and completeness of environmental and social data. These limitations stem from the nature of these data. Certain parameters rely on human behaviour and so are affected by culture and personal perception. Other parameters rely on complex measurements that require constant tuning. Still others rely on estimation and modelling. Shell accepts that our published environmental and social data will be affected by these inherent limitations. We continue to improve data integrity by strengthening internal controls. In this regard, techniques for measuring CO₂ levels have advanced significantly since we established our 1990 CO₂ base level. Recently, our internal audit function found that certain controls on our 1990 measurement do not meet current Shell standards. As a result, we are strengthening the controls on our 1990 baseline and on all CO₂ measurements.

Safety and environmental data are collected from companies and joint ventures where we have a controlling interest and certain companies to which we provide operational services. These data are reported on a 100% basis, regardless of our equity share in the company. Operations that were acquired or disposed of during the year are included only for the period of time we had ownership. Other data is collected from external sources, staff surveys and other internal sources as indicated and reported.

Data marked in the social data table is obtained from an internal survey completed by the senior Shell representative in each country. The degree of accuracy for this is significantly lower than for data obtained through our financial systems. This year, we have carried out additional checks on the figures obtained via this survey, to provide us with more confidence in its reliability and continue to tighten our internal controls on this data to improve its quality.

We set internal improvement targets for our key safety and environmental parameters and have longer-term public targets for energy efficiency in our chemicals plants, for eliminating the disposal of gas by continuous flaring, and for reducing GHG emissions from our operations.

Unless otherwise noted, the number of homes served by our activities are estimated throughout this Report on the average electricity consumption of a household in Europe and the fuel efficiency and petrol tank size of a typical small car (Ford Fiesta).

See our Group Performance Monitoring and Reporting Guide for more information.