Although not in the same tradition, but raising a similar concern as Lauderdale, Malthus and Sismondi, J. A. Hobson (along with Mummery) develops what is known in the literature as the ‘underconsumption theory’. Mummery & Hobson present this in The Physiology of Industry: Being an Exposure of Certain Fallacies in Existing Theories in Economics (1889). These themes are also expressed in other works of Hobson such as The Social Problem (1901) and Problems of Poverty (1905). This blog post completely draws from M. Schneider’s 1996 book titled J. A. Hobson (Macmillan Press; especially chapter 4). A contraction of output can happen through two different routes in a closed economy: (1) underconsumption and (2) underinvestment. The logic of this argument can be explained in the following manner. If planned expenditure ‘ consumption or investment, falls short of the planned output at the aggregate level, output levels will contract in the subsequent period of production. Planned expenditure may be less than planned output either due to planned consumption and/or planned investment falling short of the expenditure necessary to validate the planned output.
Mummery & Hobson take as their focus the first route. As Schneider writes:
‘In the underconsumption theory, a deficiency of consumption, and hence excessive saving, is seen as being accompanied by excessive investment. ‘underconsumption is simply a case of excess supply in the consumption goods market and excess demand in the investment goods market” (Schneider p. 59)
They conceptualize the economy as being made up of two sectors ‘ consumption goods and investment goods sector. Aggregate income can be used for consumption or saving. What is not consumed is saved, and this is assumed to be translated into investment. Therefore, if consumption falls (i.e., there is underconsumption) then saving and investment increases (i.e., there is overinvestment).
Mummery & Hobson assume unchanging technology. A certain amount of ‘capital’ (circulating and fixed) is required to produce the output. [No substitution between labour and ‘capital’ as in marginalist economics.] Given this specification of technology, a decrease in consumption will reduce the quantity of ‘capital’ that can be usefully employed.
‘since ‘the profits which form the money incomes of all capitalists concerned in production, the wages of all the labourers concerned’are in a regular condition of commerce, paid out of the prices paid by consumers’ (1889, p. 71), a decrease in consumption would lead to a ‘general reduction in the rate of incomes’ (1889, p. 96) or, in other words, to a ‘depression in trade’, with ‘requisites of production’, including labour, consequently becoming unemployed or only partially employed. (as in Schneider p. 62)
That is, a decrease in consumption ceteris paribus leads to a decrease in aggregate income, since expenditure falls short of output. This also leads to an increase in unemployed labour. This idea of underconsumption has to implicitly assume that investment is ultimately a function of consumption demand. Otherwise, the underconsumption does not pose a problem as it is matched by an equivalent overinvestment. This is why ‘underconsumption leads to the accumulation of excessive capital equipment’ (Schneider p. 71).
The link between aggregate consumption demand, aggregate income and saving is visible in the excerpt from Mummery & Hobson below.
‘it is precisely because they [people] are consuming more that they can save more.’ (1889, p. 126; as in Schneider p. 63).
This excerpt is also suggestive of activity levels being determined by aggregate demand, particularly, consumption demand. A higher income means that the funds to save from are higher. To put the same point differently, saving is a positive function of aggregate income.
Keynes underscored the fact that what is true for an individual need not be true for the aggregate. This is now known as the fallacy of composition.
Every ‘attempt to save more by reducing consumption will so affect incomes that the attempt necessarily defeats itself.’ (Keynes 1936, p. 84; as in Schneider p. 63).
‘Hobson’called this (misleadingly) ‘the distributive fallacy’, which ‘consists in arguing that what is true of each must be true of all’ (1916, p 9; as in Schneider p. 63).
Hobson has made significant contributions to economics. The idea that saving should be favoured over consumption is shown to be false, and this principle is to be found in Kaleckian/Keynesian economics as well. Hobson demonstrated an implicit understanding of the accelerator principle ‘ that investment is dependent of consumption (or that investment is a derived demand). Finally, underconsumption (or a deficiency of aggregate demand) leads to unemployment of labour and underutilized ‘capital’ stock.