Yes, there are complicated systems of compensation between different national pension schemes that could no doubt be usefully cleared up.

But your "50% of doctors' pension contributions for farmers and SNCF" is nonsense. Look at the document you link to:

Commission des affaires sociales : bulletin de la semaine du 18 décembre 2006		Commission for social questions: weekly bulletin 18 Dec 2006
Le bilan des flux cumulés des mécanismes de « compensation » et de « surcompensation » fait apparaître un petit nombre de contributeurs nets. Il s'agit essentiellement du régime général, pour 5,1 milliards d'euros, c'est-à-dire 6,5 % de ses produits, de la caisse nationale de retraite des agents des collectivités locales (CNRACL) pour 2,6 milliards d'euros, soit plus de 20 % de ses produits, et de l'Etat, au titre de la fonction publique, pour 1,7 milliard d'euros, c'est-à-dire 4 % des charges de pensions du budget. Sont également concernées la caisse nationale des industries électriques et gazières pour 131 millions d'euros (4 % des produits du régime), la caisse nationale d'assurance vieillesse des professions libérales (CNAVPL) pour 371 millions d'euros, soit 32 % de ses produits, et la caisse nationale des barreaux français.		The balance of aggregate flows of the mechanisms of "compensation" and "surcompensation" shows a small number of net contributors. They are essentially the general (salaried workers) system, paying €5.1 bn, that is 6.5% of its income, the local government employees' pensions scheme pays €2.6 bn, or over 20% of its income, and the State under the heading of the civil service, pays €1.7 bn, or 4% of the pensions section of the budget. Also concerned are the electric and gas industries' pensions scheme for €131 mn (4% of income), the liberal professions' pensions scheme (CNAVPL) for €371 mn, or 32% of its income, and the barristers' pension scheme.

Doctors, through their scheme (CARMF) pay into the CNAVPL, that pays 32% of its receipts to the compensation and surcompensation schemes. Which pay out to:

Commission des affaires sociales : bulletin de la semaine du 18 décembre 2006
les exploitants agricoles perçoivent en effet à eux seuls 4,3 milliards d'euros et les salariés agricoles 2,2 milliards d'euros, soit plus de 60 % des flux redistribués. Viennent ensuite les régimes des mines pour 1,2 milliard d'euros, des commerçants pour 0,9 milliard d'euros, des artisans (0,5 milliard d'euros) et de la SNCF (337 millions d'euros).		[retired] farmers alone receive €4.3 bn and farm labourers €2.2 bn, or 60% of the redistributed flows. Next come the mines pension scheme with €1.2 bn, shopkeepers with €0.9 bn, craftsmen (€0.5 bn), and the SNCF (€337 mn).

So the main subsidies concern branches of activity that have undergone demographic change that has left a small number of payers-in covering a large number of pensioners (farming, coal-mining, shopkeepers and craftsmen). SNCF only receives about 3% of the total (according to my calculation).

So making this a beef against the régimes spéciaux seems unjustified, it really involves branches whose numbers have gone down dramatically, (and not only farmers, for that matter). And the proportion of doctors' contributions is not 50%, but considerably less (32%).

And what doctors' contributions are those? Only the obligatory minimum national pensions scheme payments (doctors will contribute to other schemes that will benefit them exclusively; the national minimum is a social solidarity system). How does that pan out for most doctors? I could give you the details (from a liberal professions' tax handbook, I haven't got a link, sorry), but most will be paying the ceiling, which, for 2006 income, was €4,334. 32% of that is €1,387. These are professionals who average more than €80,000 p.a. in net (of expenses inc social contributions) before-tax income. Sob-sob.

There may be an over-complicated system that needs overhaul, but essentially this is about redistribution and solidarity (and has little to do with the régimes spéciaux, as your document proves). And, if one is worried about privilege and inequality, perhaps one should be concerned about this:

Le Monde

Doctors' (top three) income has risen faster than salaried workers (bottom line, flat for several years). This graph stops in 2004, but the trend has continued since.