The difference between a proletarian and a capitalist can be quantitatively determined.
As a general rule, a proletarian buys items that are consumed completely. For example: groceries, rent, heat, clothes, and medical care are all things that, once consumed, are gone and must be purchased again in order to reproduce those items' use-value.
A capitalist, on the other hand, buys items that are consumed productively.* For example: plant facilities, raw materials, machines, and labor are all things that, once consumed (in the production process), become items retaining their previous value as well as possessing added value (if not, why bother to be a capitalist?).
The statistical breakdown of these two classes are: proletarians 90%, capitalists 10% (of the American population).(1)
Nevertheless, there is a perceived world of difference between the 'working class' and the 'middle class'---although by the above criteria they are both proletarians.
One difference is that the middle class has higher wages (usually salaries) than the working class. Another difference is that the middle class has more education (skill**) than the working class. And, importantly, yet another difference is that the middle class has more commitment to the capitalist order of things than the working class.
Unlike the working class proletarian, the middle class proletarian does possess some items that are NOT consumed completely. Indeed, the middle class proletarian possesses 'working capital' of a sort (which can be consumed productively). This 'working capital' includes education, stock holdings, and basic savings.
The statistical verification of a middle class proletarian (in America), so characterized: 25% with a B.A. degree or higher (2); 25% owning stock (above $2,000) (3); and 25% possessing savings sufficient enough to retire at the age of 65.(4) Thus it is evident that only a quarter of the American people are college educated, own stock, and earn enough to retire. This percentage INCLUDES the previously cited 10% who are capitalists. Therefore we may deduce that the middle class comprises (only) 15% of the American people.
Whereas the working class comprises the remaining 75%.
There is another distinction that deserves attention, however.
As I mentioned before, some work occurs in the production sphere and other work occurs in the circulation sphere. Production is primarily characterized by raw material retrieval & processing and commodity manufacture & assembly. Circulation, by contrast, is characterized by book-keeping, transportation, packaging, advertising, and---especially---retailing. These are two VERY DIFFERENT parts of the overall circuit of capital (m - c - m). While the production process creates value, all the circulation process does is realize value.
Marx makes this distinction explicit:
The general law is that all costs of circulation which arise only from changes in the forms of commodities do not add to their value. They are merely expenses incurred in the realization of the value or in its conversion from one form into another.(5)
Analyzing book-keeping, Marx stated:
[I]t is palpably clear that this function and the instruments of labor consumed by it represent additional consumption of labor-time and instruments which are necessary, but constitute a deduction from the time available for productive consumption as well as from the instruments of labor which function in the real process of production, enter into the creation of products and value.(6)
Of course, book-keeping is but one example of the circulation process (as defined by Marx). Another, more pertinent example is the ENTIRE computer infrastructure of capitalist intercourse.
What Marx posited was not only does circulation NOT add value to products, but it DEDUCTS from productive capital itself.
This means that additional circulation costs (such as extended computer technology) acts as a DRAIN upon profits. In turn, to continue realizing profits at the same rate, capital must offset its increasing circulation expenses by increasing productivity (which is another way of reducing labor costs per constituent commodity) or by simply squeezing labor (in the form intensified work or reduced wages---or both).
The continual trend toward overseas manufacturing AND the 'computer revolution' evinces that capital is indeed squeezing labor as its circulation costs increase.
Returning to the subject of the middle class distinction, I think it is useful to point out that the circulation sphere comprises many levels of worker skill required. The circulation sphere is the workplace for the web designer for Amazon.com AS WELL AS the zombie standing behind the cash register. Neither add value to the product ultimately sold; both simply assist that product in meeting its buyer. But the difference TO THE WORKER is paramount. The web designer is high-wage and high-status; the cashier is but an anonymous poverty-level drone.
Ultimately the distinction is SKILL.
America and similarily 'advanced' capitalist nations are primarily service economies (i.e. circulation sphere)---while Asia and 'Third World' nations are outposts for raw material extraction & processing as well as (increasingly) manufacturing locations.
While some circulation sphere workers are skilled, many are not.
While some production process workers are skilled, most are not.
That is the proletariat's international intersection of solidarity.
Job Rotation = The End of Capitalism!
* The capitalist also purchases and consumes completely like the proletarian, i.e. caviar, summer mansions, a night at the opera, etc. However, what characterizes the capitalist qua capitalist is productive consumption ('making' money).
** Recently Nikhil Jaikumar stated: '[I]n Barry's argument, both the 'experienced' man and the college educated one are skilled workers. (I think).' This is correct. Some workers do receive education in apprenticeship situations---either formally or informally 'on the job.' These workers are statistically anomalous (and often learn skills so specific that job possibilities outside the apprenticeship situation are as rare as the opportunity afforded them). Needless to say, capital publicizes these exceptional opportunities to the utmost using the media it controls.
1. Business Week, 28 November 1994, p. 34.
2. Statistical Abstract of the United States 1996, table 243, p. 160.
3. Business Week, 1 September 1997, p. 67.
4. Forbes,16 June 1997, p. 159.
5. Marx, Capital, vol. 2, International 1967, p. 149.
6. Ibid., pp. 133-4, emphasis added.