Ah yes! BZW, I remember it well.
The index has changed 'printed ownership' over the years, but regularly surfaces under the name of some firm or another. It's always been a fairly simple index comparison in its basic form, which was to show the relative performance of cash deposits, the gilt market and the UK equity market over a very long period, with or without reinvestment of interest/dividends, and with or without an adjustment for inflation.
I suspect that originally the equity index used was the Ordinary Share Index, and at some point I think it was transformed into the All-Share Index.
Any set of statistics will inevitably have a degree of survivorship built into it, since some markets vanished completely when the country foundered financially, and any small country will no longer be considered seriously as an index for comparison purposes.
Nonetheless, I am not at all surprised that a batch of surviving investment trusts should have wiped the floor with cash, gilts or a passive equity index.
With the passage of time, the tiniest consistent % gain will magnify the results beyond belief, just as an annual 3% management charge will eventually make a portfolio value become minute.
For those investors who wish to compare a passive index with a selection of funds or a selection of investment trusts, the evidence over the last 150 years (if it does not change in the future) suggests that closed-ended ITs (which can use gearing and don't have to sell assets at unfortunate times), generally beat open-ended, non-geared funds (which have to sell to meet redemptions); these 'real assets', in turn, in times when there is any inflation, however small, beat gilts and cash, which are not 'real' assets.
I doubt if this pattern will change unless we either revert to the Stone Age or equities become so much in demand relative to any other assets that demand prices them far, far beyond sensible value.
