Assessment of economic data/information/evidence in more or less any context can raise difficult issues. Compared with the testing of hypotheses and theories in the physical sciences, there is much less ability to make use of controlled, repeated/repeatable experiments; and the resulting limitations are often reinforced by the complexity of the relationships and interactions that are involved in the determination of economic outcomes. This complexity necessarily leads to high degrees of uncertainty, particularly (though by no means exclusively) uncertainty about the future.