(Lonergan’s) massive part-time investment of his surplus intellectual energy in an effort to understand the “causes” of the Depression was a response specifically to the boom and bust dimension of that problem.  His response came in his exploration of the functional correlation between production, exchange and finance in an economy.  Central was the question, how in aggregate in an economy does money circulate?  His subsequent insights led him to divide it into distinct basic and surplus circuits causally interacting with a redistribution financial zone.  As a result he was able to show how with better financial management of that circulation the emergent standard of living of an economic community could advance cyclically to a higher level without any downward negative swings. [Mathews, 2009, 150] Mathews’ website

The economic process is a whole dynamic organic process constituted at once by dynamic production, exchange and finance, in conformity to principles and laws of concomitance, continuity, equilibrium and solidarity.

… a business cycle theory is to be found in the interpretation of the whole. (CWL 15, 8)

All science begins from particular correlations, but the key discovery is the interdependence of the whole. … While it is true that a tableau or diagram cannot establish the uniqueness of a system or rigorously ground its universal relevance, it remains that the diagram (of the interconnections of a few precise aggregates) has compensating features that Quesnay’s system of simultaneous equations may imply but does not manifest. … There is the tremendous simplification (a diagram) effects. … The aims and limitations of macroeconomics make the use of a diagram particularly helpful, …  For its basic terms are defined by their functional relations.  The maintaining of a standard of living is attributed to a basic process (distinct process 1), an ongoing sequence of instances of so much every so often.  The maintenance and acceleration (distinct process 2) of this basic process is brought about by a sequence of surplus stages, in which each lower stage is maintained and accelerated by the next higher.  Finally, transactions that do no more than transfer titles to ownership (distinct process 3) are concentrated in a redistributive function, whence may be derived changes in the stock of money dictated by the acceleration (positive or negative) in the basic and surplus stages of the process. … So there is to be discerned a threefold process in which a basic stage is maintained and accelerated by a series of surplus stages, while the needed additions to or subtractions from the stock of money in these processes is derived from the redistributive area. … it will be possible to distinguish stable and unstable combinations and sequences of rates in the three main areas and so gain some insight into the long-standing recurrence of crises in the modern expanding economy. [CWL 15, 53 and 177]

See Understanding All in a Unified Whole.

More positively, the channels account for booms and slumps, for inflation and deflation, for changed rates of profit, for the attraction found in a favorable balance of trade, the relief given by deficit spending, and the variant provided by multinational corporations and their opposition to the welfare state. [CWL 15, 17]

 positive or negative transfers to basic demand (D’-s”I’) and consequent similar transfers to surplus demand (D”-s”I”) belong to the theory of booms and slumps.  They involve changes in (aggregate basic or aggregate surplus) demand, with entrepreneurs receiving back more (or less) than they paid out in outlay (which includes profits of all kinds).  The immediate effect (of these aberrational monetary transfers) is on the price levels at the final markets, and to these changes (in price), enterprise as a whole responds to release an upward (or downward)  movement of the whole economy.  But the initial increased transfers to demand [that is, excess transfers along (D’-s’I’)  and (D”-s”I”) ] are not simply to be supposed.  For that would be postulating without explaining the boom or slump. [CWL 15, 64]