Given the evolution of the capitalistic society, to what degree is Marx's model of capitalist society no longer valid nowadays ?
Are there any authors which discuss the contemporary validity of Marx's work ?
A political economic system is a set of ideas, habits and institutions that purport to solve problems when people deal with one another. For example, if I would like my house to be painted there are a number of potential solutions to that problem. I could get somebody else to do it. I could get paint and do it myself. I could change my preferences so that I no longer want my house painted. And there may be other solutions, e.g. - I should paint some rooms and not others. So there is a problem to be solved: how can I and other people come to agree on those issues that we have to agree on for me to paint my house or not paint it or whatever?
The free market way to solve this problem is to allow people to bid for resources, like paint, ingredients for paint, a house painter's time and so on. If I can reach an agreement on resource X with its current owner, I will buy it, otherwise I will not.
Marx pointed out what he thought were flaws in this way of doing things. Some people called capitalists paid other people to do stuff with equipment they owned. He alleged that the value of a particular item had something to do with the amount of labour people had done to make it. The capitalist wasn't working on whatever widget the worker made with his machinery, so he was exploiting the worker by getting some of the value of his labour.
Now, if it was true that the value of an item is dependent on the amount of labour alone, then it would always have to be true. For if this were to change then there would have to be some explanation of the change and that explanation would contradict the labour theory of value because it would say that sometimes the labour doesn't determine the value. So there is no question of saying that Marx is right at some times and wrong at others. Either he is right or he is wrong and that does not change over time.
However, as early as 1898 the economist Eugen von Böhm-Bawerk published a criticism of Marx's ideas pointing out lots of problems with them:
For example, not all work is the same. Would you pay a brain surgeon the same amount for an hour of his time as you would pay a cleaner? No. If you want a brain surgeon's services you're willing to pay a hell of a lot more than you would pay for a cleaner.
There are other problems with Marx's ideas. Marx was in favour of violent revolution to replace what he claimed were bad systems of political economy:
In depicting the most general phases of the development of the proletariat, we traced the more or less veiled civil war, raging within existing society, up to the point where that war breaks out into open revolution, and where the violent overthrow of the bourgeoisie lays the foundation for the sway of the proletariat.
As Karl Popper pointed out in The Open Society and Its Enemies, violent revolutions are a bad idea except in cases where non-violent ways of dealing with disagreements do not exist, for a description see:
Marx's economic and political ideas were wrong and they still are and they always will be.
From Mandels introduction to Capital - Volume 1:
What Marx explained, however, was above all, the ruthless and irresistible impulse to growth that characterises production for private profit and the predominant use of profit for capital accumulation.
Certainly, the growth of capitalism has been spectacular - when Capital was first published Capitalism was restricted to North Europe whereas it is now the dominant economic mode globally; hence one can say that this prediction of Marxs has been verified; the question is his explanation sufficient.
The concentration of wealth & power in a small number of giant industrial & financial corporations has brought with it an increasingly universal struggle between Capital & Labour.
Capital & Labour are technical terms in Marxist theory, and refer, to a first approximation, to ownership of the means of production; conventionally of course an owner of a factory is 'labouring' as much as the workers in the factory - the owner works; but the workers do not own the factory - the means of production. It is also a historically conditioned term, one doesn't think of the economy of the Roman Empire or the classical Islamic Empire as capitalist; it is also conditioned by what is produced - the commodity; and one expects that a large part of the growth of the economy is produced by commodification of new or larger areas of the natural economy. For example, the commodification of mortgage and other consumer debt, aka securitisation in the last business cycle.
An economic theory based on the historical relativity of every economic system, its strict limitation in time...[shows] that Capitalism itself is a poduct of history. It will perish in due course as it once was born. A new social form of economic organisation will then take place of the capitalist one: it will function according to other laws that govern the capitalist one.
Marx distinguishes the capitalist regime from the regime preceding it, that of petty commodity production, and to that of the future one. His essential observation is a trivial one - that all things pass away. The question is has he mapped out the conditions that lead to a structural instability and how to identify it.
With the industrial revolution and the emergence of the modern factory, this process of the submission of labour to capital in the course of the process of production is rooted, not only on the hierarchical forms of labour organisation, but in the very nature of the production process itself.
Marx says here what is called the division of labour in classical terms is a function of the factory - labour becomes part of he production process by becoming commodified.
No part of Marxs theory has been more assaulted in the academic world during the last seventy-five years than his theory of value...this theory is indeed the corner-stone of the whole system...from a quantitative point of the value of a commodity is determined by the quantity of simple labour, from a qualitative point of view it is determined by abstract human labour.
Here Marx is using quantitative & qualitative in a special way; it would be better to have said that the first is superficial and the second deeper. Looking at Hume is-ought problem on the question of the provenance, the gap between what is the case and what ought to be the case; a situation resolved by Hume in his psychology; we see this as the origin of moral values; in this form one can also ask what is the origin of economic values - the apple on a tree nor the oil on a ground comes with a price-tag - one can go back to Hume here, by analogy, and say tat it is rooted in human psychology, and the measure of this via Marx is labour; classically it is determined by scarcity; but one notes here that labour is in a positive relation to scarcity; what is very scarce takes a great deal of labour to obtain. For example a diamond is valued because it sparkles and is beautiful (the psychology), they are hard to find (scarcity) and hence costs a great deal to extract (labour). One ought to note, that at least philosophically, that all labour should count; and this means that of the mine-owner as well as that of the miners, and those who transport them - thats why this labour is called socially abstract.
One should separate Marxist philosophy & politics: Capitalism is associated originally with the West, with the rest of the world in one form or another politically under its subjection; generally the anti-colonial movement rallied under various forms of nationalism and socialism (one supposes that they didn't wish to identify with the economic or political form of their subjection) and was generally successful after the weakened state of the West after the two World Wars in the early 20C.
A general criticism, originally associated with Hayek,is the efficiency of free markets as opposed to that of command economies; this is of course correct, and also besides the point - Marx was interested in the general laws that govern and not determine the economy.
Marx as a political activist may or may not have advocated violent revolution; but it is quite clear that he understood that economics cannot in philosophical terms be separated out from violence:
In actual history, it is a notorious fact that conquest, enslavement, robbery, murder in short force play the greatest part...as a matter of fact, the methods of primitive accumulation are anything but idyllic.
One suspects that he would have forseen that the growth of Capital to global dominance would be accompanied by violence.
Finally, one suspects Marx was motivated by the immediate conditions of the newly industrialised England that he could see around him:
All the phenomena of the factory districts are reproduced here, including a yet higher degree of disguised infanticide and stupefaction of children with opiates (Public Health, 6th Report)
In general terms, Marxs theory seems to have been borne out empirically; this doesn't mean that there are parts of his theory that will be wrong or evasive - there will be; but enough is true that its worth understanding exactly how it fits together.
Its also worth adding that the social democracies of Europe can be seen as non-capitalistic because of the use of progressive taxation; they can be seen, in Marxs terms, as a synthesis of 19C pure capitalism, with the antithesis of communism to synthesise the current political consensus; but with increasing globalisation, one might expect a similar but also very different regime globally - the notion of a global civil society.
Negri & Hardt analyse this motion in their triplet of books - Empire, Multitude & Commonwealth; Empire is the regime of Capital in its global situation (thesis), Multitude is the response (anti-thesis) and Commonwealth (synthesis).
I think the main difference between the Marx's time and now, is that our present economic system is a mixed economy, which blends parts of the capitalist system (e.g., substantial private ownership of the means-of-production, relatively free trade, etc.) with parts of the socialist "planned" economic system (e.g., substantial state ownership of the means-of-production, state intervention in the economy, etc.).
Since our economic system is an unstable mixture of both economic systems, quite a bit of what Marx said about capitalism would still be relevant today (though I do not assert its correctness). There are certainly aspects of his model that have been clearly falsified - e.g., the fact that the working class have become richer, in real terms, and are not the "revolutionary" class he claimed they would be (empirically they are less in favour of socialism than the "elite" classes).
With regard to contemporary authors who discuss the application of Marxism to the modern mixed economy, there has been quite a bit of work on this. You can find a book-length treatment of this topic in Mattick (1969) and a shorter article by Davis (2010). You can find a modern Marxist critique of market relations in McNally (1993). There is plenty more, but that should get you started.
Marx's magnum opus was "Capital: Critique of Political Economy"; it was supposed to be-among other things-a critical review of contemporary economic theory which was then called Political economy. Classical political economy ie the body of research by eg Malthus, Ricardo, Smith, Marx was eventually superseded by the so called marginalist school of thought. What goes by the name of economics today is traceable to the works of Jevons, Menger, James Mill, Walras etc who had made seminal contributions to the research program of the marginalist school. That is to say that Marx's intellectual work as far as economic theory is concerned is a part of the intellectual history of economics. Political economy was superseded by economics and marxist political economy was simply incompatible with the new ethos.
Anwar Shaikh is an economist at the New School who contends that modern capitalism is better understood using the tools of classical political economy instead of what modern economics has to offer. He has recently published a book along these lines.
According to Marx's view history progresses in successive steps which he calls 'modes of production'. Each mode of production, is characterized by available means of production and the relevant social relations that their ownership entails. Eventually, the development of the means of production becomes out of sync with the prevalent relations of production which eventually turn from facilitators to obstacles of development. The impasse is overcome by the introduction of a new mode of production.
Mark Blyth is a professor of international political economy at Brown University (not-a-Marxist). Recently he published a paper where he purports that what has ensued after the Great Recession of 2008 can be explained by recourse to regime swifts reminiscent of the regulation school. The regulation school builds upon the the notion of the mode of production.