This is an ambitious and important book. Its title annexes the notion of revolution, advocated by Syme in The Roman Revolution (1939). In this, K. follows Wallace-Hadrill's major study, Rome's Cultural Revolution (2008), by aiming to round out our appreciation of that watershed. ‘The present work’, K. writes, ‘compliments these types of account by detailing and offering an explanation of the fundamental economic changes that occurred in the Roman world of the second and early first centuries bc. Without an understanding of this economic revolution’, he argues, ‘the contemporaneous political and cultural changes in Roman society cannot be fully comprehended or explained’ (p. 7). But ‘contemporaneous’ is perhaps modest. K. is consistently clear that his focus is on the second to mid-first centuries b.c. By 50 b.c., he has largely told his story. Yet Caesar had not crossed the Rubicon; Octavius was barely into his teens; and Syme's account had filled only three of his 33 chapters. At that point, too, much of the ground covered by Wallace-Hadrill still remains in the future. What K. is offering, though reticent of saying so, is to a considerable extent an account of the sine qua non for other aspects of the revolution.

That is not the only big subject to peer out from K.'s pages. His introduction is subtitled ‘The Creation of Complexity’; and he suggests of his material that ‘the plausibility of a “non-Finleyan” Roman world is greatly enhanced by an understanding of these developments’ (p. 7). His chapters are plainly intended to resonate, including as they do such topics as ‘Credit and Financial Intermediation’; ‘Trade, Capital and Interconnected Markets’; and ‘After the Credit Crunch’. Just as Syme consciously evoked the sinister rhetoric of the 1930s, and Wallace-Hadrill has evoked the ‘consumer revolution’, K. is unafraid to pinpoint similarities between ancient and modern experience. In the present case, we are dealing with the manner and extent to which an influx of wealth, triggered by Roman empire-building, generated a different order of economic sophistication, which would remain in place until the downturn of the post-Roman West.

K. develops his argument in three substantial parts, totalling nine chapters, plus a long final chapter. The first part concerns ‘Sources of Revenue’. With a quantitative eye on the scale and cost of Roman military activity, K. offers positive evidence to show that Rome's empire-builders were well aware of the financial implications and, at times, let slip an expressly pecuniary motive (pp. 28–9). He estimates that, between about 200 and 150 b.c., Rome secured through booty and war indemnity ‘nearly 46,000 talents … equivalent to 1,050 tonnes of silver’ (p. 42), with military commanders as the principal immediate beneficiaries but with flows of cash to the wider military and the economy as a whole. Yet this would be eclipsed by the revenues from Spanish and Macedonian mines. Support for a measurable increase in smelting activity comes from isotopic analysis of lead in Arctic ice cores, and from radiocarbon dating (pp. 46–9), helping K. to take seriously Polybius’ report on the scale of Spanish mining – ‘equivalent to approximately 35 tonnes of silver per annum’ (p. 58). C. Gracchus emerges from a significant discussion of the lex Sempronia de provincia Asia as the architect of the first true attempt at state budgeting, matching revenues to expenditure (pp. 59–83).

K. goes on, in the second part, to examine ‘The Roman Money Supply’. Not only had Rome acquired mining revenue but provincial revenues in general, before Pompey's conquests, can be estimated at ‘perhaps 190 tonnes of silver per annum’ (p. 87, with pp. 72–3). Alert to debates on die productivity, K. accepts that much bullion became coin, with a dramatic increase in circulation (pp. 89–93) – prompting discussion of the geographical reach of the booming denarius and the increasing desirability of silver coin over bronze in an inflationary context (pp. 93–104). Taking the argument an important step further, he discusses the rise of ‘a mechanism for the creation of money beyond the available supply of precious metals’ (p. 107). That is to say, bankers and credit. The model in K.'s telescopic sight is that of Finley, ‘who simplistically asserted that the money supply in the ancient world was essentially inelastic because of its reliance on coin and the lack of “machinery for credit beyond the lending of coins”’ (p. 108, quoting Finley's The Ancient Economy). K. brings a distinctive flair to the subject, starting with a superb ABC on how a deposit bank creates assets through loans (pp. 110–12). This leads to scrutiny of the evidence for credit banking (pp. 113–27). He concludes that, ‘far from … “the absence of credit-crunching instruments and institutions remaining as an unshaken foundation of the ancient economy”, Roman argentarii did create credit and money, pecunia, beyond the available supply of precious metals’ (p. 127, again quoting Finley, The Ancient Economy).

In the third part, K. addresses ‘The Application of Funds’. A long chapter on ‘Investment Farming and Agricultural Exploitation’ develops a series of clearly-drawn views. The early growth of great estates was confined to central-western Italy, where it still did not preclude smallholdings. This was linked with a rise in the export of amphorae, in particular Dressel 1 and latterly Lamboglia 2, in conjunction with a rise in wine production and possibly also olive oil and other soft commodities. We are dealing with the rise of ‘market-oriented agricultural production’ (p. 144) which led to commercial shipping investment (pp. 145–6). This chapter also covers investment farming by absentee landlords; investment in technology; the agrarian crisis of 133 b.c.; public land; the peasantry; demography; and slaves. It culminates with some striking observations on privatisation: ‘what the Gracchi started was a process of denationalization and privatization, with the period from 133 to 111 being crucial in the transformation of arable ager publicus into private land’ (p. 184). In this, the ‘main losers’, K. points out, ‘were the Italian allies, since it is clear that much of the public land that was assigned after 133 lay within the boundaries of Latin and allied states’ (p. 185).

Subsequent chapters point to the investment of substantial capital in Asia and Delos, explored by way of an alert untangling of the implications of the attack by Mithridates VI of Pontus in 88–87 b.c. (pp. 189–213); to the rise of the construction and manufacturing industries in Rome and Italy (pp. 215–34); and to a ‘credit crunch’ in the 80s b.c., brought on by the Social and Mithridatic Wars, in which the interlinking of financial markets in Asia and Rome is highlighted (pp. 235–65, especially 245–6). This credit crunch, K. tentatively suggests, might have shifted the balance from deposit banking to aristocratic financiers, stifling further banking growth.

A long concluding chapter (pp. 269–325) addresses the problem of quantifying real per capita economic growth through several methodical calculations. Acknowledging ‘the inherent fragility of our estimates’ (p. 324), K. none the less makes some proposals for the century between 150 and 50 b.c.: a price rise of 95%; real GDP growth of 72% (0.54% annually); a real fivefold increase in elite wealth; and a real 77% increase in non-elite free wealth.

K. is acutely aware of the provisional nature of his detailed arguments (e.g. p. 297: ‘crude, back-of-the-envelope efforts’). But his approach is lucid and serious, often carrying conviction. Alternative views will need to show the same precision. His closing ‘Summary and Conclusions’ largely repeat the chapter conclusions (with some near-exact replication of phrasing, from pp. 82–3, at 331). As a result, it is both a strength and a limitation that this treatment of the economic revolution is self-contained: its relation to the cultural and political revolutions of the age remains to be developed. But K. has provided a major building-block.