Every now and again, some appalling new statistics come out. Twelve rich people have more wealth than the entire population of three continents. One repellent American family spends more on foie gras than African countries spend on HIV medicine. And so on. I embellish, but not by much. Such astounding figures, the orders of magnitude, defy a sensible response. What does one do with such information?

Today's statistics from Oxfam fall into the same category: the five richest families in Britain have more wealth than 12.6 million Britons put together. Next to such staggering realities, Oxfam's proposed response is strikingly mild. Close tax loopholes, support a living wage, consider a wealth tax. These are decent enough measures in themselves, but it would be useful just occasionally to break down the social meaning of such information, and work out a response on that basis.

Oxfam's figures are essentially about the class system. They are more enlightening than usual, because they focus on wealth rather than income streams. Even so, the status of such figures is not clear.

First, because there is a difference between the wealth of the poorest, which largely consists of the things they need to survive (above all their home), and that of the richest, which largely consists of liquid assets and luxuries. Second, because much wealth is effectively hidden: the super-rich often stay well out of sight, rather than parading themselves and their gains.

One effect of widespread tax avoidance is precisely that much of the wealth is simply not registered by official data. This is particularly the case for inherited wealth. In all likelihood, the structure of wealth ownership is far more polarised than the statistics suggest. However, wealth inequality is not in and of itself the class system; it is, rather, one of its outcomes, a snapshot of a process that we really need to understand in its totality. Like a bodily symptom, growing inequality is an outcome, a manifestation, of processes that go much deeper.

Why should the rich perpetually get richer? According to the dominant ideology, getting rich is a reward for hard work and the intelligent disposal of resources. But this is a crude morality tale that infers moral rectitude from market success. Even if it were true that the rich are hard working, this wouldn't distinguish them from most people who lack the proverbial pot to micturate in.

Look instead at the five families identified by Oxfam. The greatest advantage enjoyed by these people over anyone else is not their ability to work, nor their intelligence or effort. It is the measure of strategic control they exert over the assets, productive apparatuses and markets through which the production and ownership of wealth is organised. They either possess property, own factories or dominate commercial markets. This isn't a moral fact, but a social relationship backed up by legal and political coercion. Those who control the means of production get to appropriate the surplus wealth produced through its use, regardless of who actually produced it. And because capitalism is a dynamic, expanding system for most of the time, the amount of surplus wealth they can appropriate keeps growing too. The rich get richer.

The Duke of Westminster. Photograph: David Gamble/TopFoto

There are, moreover, certain features of the neoliberal era that impact on the form taken by class dominance. In neoliberal times, with property-driven speculation keeping the City of London riding high, the value of property in London has doubled in value to £1.24tr in the past decade. It is therefore predictable that the family of the Duke of Westminster, the Reuben Brothers and the Cadogan Family, all acquire a significant amount of their wealth from the ownership of prime real estate, where the highest-end commerce is based.

Another aspect of the neoliberal era has been the growing dependency of leading capitalist economies on speculation and debt. This is not simply a case of a few naughty bankers; it is a system in which the majority of people are incorporated, whether buying a house or a new car, or paying off student loans. Most people have become dependent on debt to some extent, while "the 1%" live off speculation on the debt. One result of this, it was found in 2007, is that the top 10% of Americans possessed 80% of all financial assets, while the bottom 90% held 73% of all debt. Unsurprisingly, much of the wealth held by these richest families is held in financial assets.

Ownership of wealth is simply one indicator, one aspect of a relationship of class dominance. And therefore, whatever happens to Oxfam's proposals, the question posed by such staggering statistics as it has shocked us with today is: why should so few people control such stupendous resources, productive assets and property? What advantage is there to a society in allowing them to have it? And how might we relieve them of it?