There is another way of comparing pension systems: by measuring the proportion of the economy they account for, and the structure of pensioner incomes.

The proportion of gross domestic product represented by the cost of providing state pensions is a good indicator of the overall ‘generosity' of state pension systems.

In 2005, the OECD average was 7.2% of GDP (reflecting growth of 16.4% since 1990). Many European countries had percentages much higher than this average figure: France (12.4%), Italy (14%), Germany and Poland (11.4%). Others, like Sweden (7.7%) and Spain (8.1%) were closer to the average.

On the other hand, several countries devoted a relatively low level of GDP to paying pensions: this was the case in those countries where the role played by private pension funds is most developed, like the United Kingdom (5.7%), Ireland (3.4%) and Denmark (5.4%).

However, it is important to bear in mind that in the case of these systems, the state generally provides guarantees and tax incentives for pension savings contributions. As a result, the amount of public expenditure devoted to pensioners is therefore higher in these countries than these figures may suggest, so when every aspect of public and private pensions-related expenditure is taken into account, the resulting levels are much closer to those seen in France and Germany.

More significant still is the structure of the income received by over 65s: what proportions of the revenue received by this age group are accounted for by state pensions, savings and investment income and earned income in each of these countries? In other words, what are pensioners living on? Once again, situations vary very considerably. French pensioners receive 85% of their income from state sources; this is the second-highest figure in Europe, after Hungary. In Sweden, Spain, Italy and Germany, the corresponding proportion is around 70%. In the United Kingdom, Ireland and The Netherlands, it falls to 50%.

So where does the rest come from? The proportion contributed by earned income is also extremely variable, and reflects the diversity of situations experienced by pensioners in the workplace. In France, the over 65s receive 6.5% of their income from employment, compared with 10% in Sweden, 12% in Germany and the United Kingdom, more than 20% in Poland and Ireland and 24% in Italy and Spain. The level of income from savings and investments is naturally high in those countries where private pensions are most prevalent: around 40% in the United Kingdom and The Netherlands, 21% in Sweden and 15% in Germany, but only 8% in France.

The enormous diversity of European systems therefore makes it extremely difficult to compare systems and reforms in any meaningful way. The French model seems to have most in common with that operated in Germany (high overall level of state provision, full pension retirement age of 67 and a long period of contributions required for early retirement), with less recourse to capitalization and better coverage for the poorest in society - against a more dynamic demographic background.