This looks like boom and bust to me.
The red line indicates the level of FTSE when Brown took over the management of the UK economy. Eleven years later, the FTSE is below the level it was back in June 1997. The index has been through at least two unsustainable booms followed by two nasty crashes.
In contrast, the period between 1984-97 looks like an Arcadian golden age of steady price appreciation, and no major crashes. Even the 1987 nosedive looks like a temporary blip.
The message is clear; New Labour is bad for equity markets, the Conservatives bring stability, and steady capital growth. Ok, I am being a little provocative here, but the chart does seem to suggest this basic message.
Also, for those of us who don't actually own equity and would like to see a more equitable distribution of wealth, the fact that the index is below its 1997 level might be a positive thing. It might give a brief moment of envious and bitter pleasure. It serves the rentier class right.
(Many thanks to Nick, who inadvertently suggested this chart to me)