This is the second (and last) “easy” post in our series, as Chapter 1 is coming up next week!
Prefaces allow authors to put their work into context, so they provide some insights to the author’s thoughts on contemporary questions. Last week, I wrote some notes and comments on the 1890 Preface.
The 1920 Preface is for the eighth (and last) edition of Principles of Economics (PE) as Alfred Marshall (AM) died in 1924.
AM begins by admitting that his original plans for a second volume were over-ambitious in the context of changes driven by industrialization (and his own poor health). His Industry and Trade (1919) gave him 900+ pages to discuss new and different topics.
Marshall claims, again, that economic evolution is gradual rather than abrupt. Not even innovations or surprises are abrupt when one can see them as the result of unrelated and untracked ideas that “snap” together after years of development. AM notes that most economics should deal with continuous evolution whereas spasmodic shocks are rare enough to leave for later study.
(This comment comes a decade before the Great Depression put “shock” in the middle of politics and economics. I am not sure if Marshall would have changed his opinion, but various editions of PE were published amidst other market crises, so perhaps he will explain their origins in longer-running trends.)
AM explains that competition and firmly established monopolies are “normal” enough for PE whereas efforts to overthrow market orders or change policies belong in a study of “superstructure” that PE ignores. I’d say those latter activities belong in a study of political-economy, i.e., when rules and institutions affecting markets are in flux.
AM then explains how economics should take its cues from biology rather than mechanical mechanisms, but that a book dealing with foundations (such as PE) must use many mechanical ideas to convey basic concepts. In this context AM says that ideas of “equilibrium” are convenient for discussion but oversimplified when it comes to understanding real (biological) market dynamics.
(Sadly, many current economics students spend too much time on finding equilibria and too little on the dynamics that move equilibria.)
AM then introduces “partial equilibrium analysis” (one of his major contributions to economics), which means looking at a few interactions while “holding all else equal,” i.e., freezing the role of other factors to make it easier to understand just a few interactions. AM notes that this “device is a great deal older than science” [p xiii].
AM then explains how this simple model of the world can be expanded — holding less and less equal — to give more insights into “change and progress… of living force and movement” [p xiii].
AM then jumps into the returns to land (agriculture) versus the returns to labor and capital (industry). He says that productivity resulting from industry and trade has “suspended” the diminishing returns problems that worried Malthus and Ricardo. AM says “suspended” because it is still possible that increases in population (“even at a quarter of its present rate”) would bring back diminishing returns.
(These statements fall into current discussions of sustainability, which is aided by technological advance but undermined by population and affluence.)
Extending further his thoughts on time and dynamics, AM explains how he uses “marginal analysis” (thinking of new actions in the context of prior actions and their results):
[T]his notion of a margin is not uniform and absolute: it varies with the conditions of the problem in hand, and in particular with the period of time to which reference is being made. The rules are universal that, (1) marginal costs do not govern price; (2) it is only at the margin that the action of those forces which do govern price can be made to stand out in clear light; and (3) the margin, which must be studied in reference to long periods and enduring results, differs in character as well as in extent from that which must be studied in reference to short periods and to passing fluctuations [p xiv].
Some of you may be shocked by (1), given that economists often say “price equals marginal cost in competitive markets,” but that statement is only true in the short run in which fixed costs are not relevant. In the long run of a few months or more, prices equal to marginal costs would not produce enough revenue to maintain capital, which means either bankruptcy or higher prices. It is thus that “the notion of margin is not uniform,” and AM’s focus on time finds its proper context.
AM then predicts that those bringing differential calculus (the mathematics of small changes) from physics to economics will have a greater role in “that limited but important field of economic inquiry to which it is appropriate” [p xv]. It is a pity that AM does not define “appropriate” since some economists use calculus everywhere.
Marshall ends the Preface by thanking his wife and many colleagues. I was interested to learn that his wife also taught economics but was not allowed (as a woman) to graduate from Cambridge. Her husband’s opposition to women participating in economics shows that brilliance has limits.
Next week: Chapter 1.