Among the 35 companies in this group, there are probably no more than half a dozen worth a closer look. The market valuation of the whole group is at present around pounds 3.5bn including two giants, Eurotunnel and Euro Disney. Most of these stocks have been floated in the past two years, though a few date back to the late 1980s. So far none has come good to any great extent - the combined profits of the group to date are, in effect, zero.
Blue-sky enterprises also consume money at a furious rate. It could be said that putting money into them recalls the famous description of owning a yacht: as being like 'standing under a cold shower tearing up pounds 5 notes'.
There are two reasons why the stocks are so weak. One is that the two giants, Eurotunnel and Euro Disney, have proved disastrous so far. The second is the generalised bear phase in the stock market. Almost by definition, these stocks reflect investor optimism and suffer on an exaggerated scale when the bullish temperature is falling.
This suggests that there could be an equally dramatic recovery when the stock market recovers. My guess is that a worthwhile across-the-board recovery will only occur if some of the hopefuls turn into genuine winners.
Many concept stocks are in the biotechnology sector. In this respect, the UK has followed the US experience. The portents are not too hopeful.
Biotechnology stocks in the US are finding it increasingly difficult to raise new money because there have been so few successes. Two companies, Amgen and Genentech, have market capitalisation around the pounds 5bn mark, and one or two others have done reasonably well for investors. But that is from a starting field of hundreds of would-be Glaxos.
Ian White, an analyst at Robert Fleming Securities, points out that worldwide there are about 300 quoted biotechnology companies and around 300 compounds undergoing clinical trials. Historically, one in every eight or 10 of these compounds is destined to become a commercial product. If we assume that each company has one drug in trials, then we can see that only around one in 10 is going to come up with a commercially successful product.
His advice is that the whole area is a minefield for investors who are neither doctors nor working in the pharmaceutical industry. Exposure is best obtained for non-experts via a managed fund, such as Rothschild's Biotechnology Trust.
The reason why investors keep coming, in the face of such off-putting odds, is that very occasionally, like companies exploring for oil and minerals, one hits the jackpot. Two companies fairly well down the route to turning their concepts into real money are ML Laboratories, with its kidney dialysis solution that has successfully passed through all clinical trials, and Tadpole Technology, with its high-powered computer workstation.
Both shares are standing closer to their 'highs' than their 'lows' at 189p and 356p respectively. Shares in ML Laboratories have weakened recently, after a hefty sale by a large stockholder, Kevin Leach.
Tadpole has also tested the enthusiasm of its City fan club by always being next year's story. But the story is a good one. Most recently the group has won an order to supply its portable workstations, based on the Risc chip, to the US Airforce. There are hopes that this could lead to further military orders from the US military and other Nato countries.
Analysts are looking for a further loss of around pounds 1.5m for the year to 30 September 1994 but a profit of between pounds 6m and pounds 10m for the current fiscal year. That would put a rocket under the share price, which presently values the group at pounds 90m.
Two exciting contenders for investors who want to defy the general odds and have a go are British Biotechnology Group (BBG) at 587p and Magnum Power Selection at 67p. BBG has a compound, Batimastat, which is in Phase 3clinical trials to test its efficacy as a treatment for the liquid retention that is a late symptom of ovarian cancer. If these are successful, the drug could be on the market late in 1996 or early in 1997.
If Batimastat proves helpful in treating ovarian cancer, it is also likely to be useful against a wide range of other cancers - and this is what has driven the share price to its current peak. With 6 million cancer sufferers in the US and Europe, the group could have a blockbuster.
Magnum Power Selection, a recent flotation capitalised at pounds 28m, has a simpler but arguably even more exciting story. It is developing a patented process for protecting computers from power-supply interruptions. This is so cheap it could be fitted by equipment suppliers like IBM and Compaq in all their PCs. The potential rewards, as calculated by stockbroker Henry Cooke Lumsden, beggar the imagination.
The bear case scenario projects pre-tax profits of pounds 12m by 1999 against a bull case projection of more than pounds 80m. For investors who like to bet on a single number when they play roulette, the shares have undoubted appeal.