At about the time I was born, two US professors looked at how gearing affects the value of a firm. They discovered that like a lot of "businessman's economics" the idea that shareholder value could be improved by the firm taking on any particular amount of debt was flawed. This is a blindingly simple insight as the discussion in Wikipedia makes clear. The two professors' names were Miller and Modigliani. Imagine two firms, identical except in respect of their capital structure. One geared, the other one not. The returns to an investor will be the same given that an investor can choose to gear his own investment in the ungeared firm by forming a portfolio composed of the equity combined with the appropriate number of bonds.
Of course governments continue to incentivise firms to gear by giving special tax advantages to debt finance relative to equity finance for reasons which are quite incomprehensible to me and clearly didn't help in creating the current fine mess we've gotten ourselves into. In principle an investing company (e.g. an investment trust) could itself benefit from the interest payments it makes on debt finance so presumably the theory actually may be valid in the presence of taxes.
The idea that risk is a knob that can be twiddled by the investor is one of the key insights which go into Modern Portfolio Theory which concludes that the market portfolio gives the best tradeoff of risk and return, and that any desired level of risk can be obtained by simply gearing it up.
The funny thing is that both these theorems, which seem pretty watertight to me, are dismissed by most real world practitioners of investment, because if market professionals behaved as if both of them were true there would be a lot less in the way of fees paid to the financial sector, both for those who arrange debt finance for companies and those who manage investments for clients.
To my mind this shows that the insights of Public Choice Theory are applicable to the financial sector. The sector behaves the way it does because of the strong incentives felt by the relatively small number of practitioners in it, even those incentives result in a net cost to the large number of savers and borrowers that the financial sector intermediates between. It seems clear that these perverse incentives have resulted in major misallocations of capital in the economy, e.g. from savers to unbankable US and UK housebuyers.
Politicians talk about new regulations so that this crisis will never happen again. I think it is pretty clear that they will miss the true cause of the crisis, because the lobbying group that benefits from the current structure of the industry is much better financed and organised than any group that ordinary providers and consumers of capital could possibly be. Committees will be set up which employ the very professionals who caused this crisis, do not understand why it arose, and who will propose the kind of detailed procedural regulation that creates large barriers to entry (and therefore ensures large economic rents to the financial sector) just like the mass or financial sector regulation that has been enacted in the past.
John Kay understands all these things and has recently written about Miller and Modigliani in the FT: Surplus Capital Not for Wimps After All. So does his former co-author Mervyn King, I'm sure. Kay also understands that regulation will simply not work, so he's definitely not going to get a call from Alistair Darling.
