The Historical Trend — 1919–57

It was not until the Second World War that economists began to measure market structures in Britain. For many years the partial nature of the data — and the lack of a clear understanding of the characteristics of appropriate measures — left a good deal of room for disagreement about the magnitude and direction of the long-run trend in concentration. Despite the fairly obvious facts that Victorian industry had been characterised by many small competing firms and that the modern economy was dominated by large ones, the available statistical studies were so imperfect that it was possible (though not very plausible) to argue that the first half of the century had seen little increase in concentration levels (e.g. Hunter 1969). More recently, as we have seen from Figure 1.1, the picture has become clearer. There is still room for disagreement about trends over the short term, but there is no doubt that the share of the largest 100 firms is substantially higher now than it was at the turn of the century. Before the 1960s the most conspicious period of rapidly rising concentration in the twentieth century was the 1920s, and we chose this for our pilot investigation using our suggested range of concentration measures.