Industry forecasters at Experian followed their rivals and cut expectations of construction activity over the coming three years.

The predicted decline in output in 2009 is now put at 7.8% followed by a slight drop of 1.7% in 2010 and a bounce back up of 1.6% in 2011.

This puts the peak-to-trough fall at around 10% compared with about 5% expected when Experian last forecast in the winter.

But despite the downward revision the forecast released today paints a very much less apocalyptic future for the industry than presented by both the Construction Products Association and Hewes & Associates.

The Construction Products Association puts the peak-to-trough fall during the current recession at more than 15% and Hewes at near 20%.

Much of the difference in the numbers for this year lies in the assumptions taken over the giant commercial building sector.

Experian sees a far shallower drop in commercial work of about 15% in 2009.

Overall the Experian forecast paints a far less gloomy picture of most sectors and is far more optimistic about the infrastructure sector, which it sees as growing rapidly.

The apparently large disparity in the figures between the three forecasts released over the past week or so is a clear sign of the high degree of uncertainty in the market.

A slight shift in emphasis within assumptions made can cause quite dramatic changes in the forecast figures.

For me this disparity illustrates the need for business planners and strategists in the industry to look very closely at the assumptions made for each sector and sub-sector in each of the forecasts. It is here where the real value lies in the forecasts.

It may be simpler and less taxing to close your eyes and take a leap of faith, but it is more sensible, in my view, to examine the scale and likelihood of risks before you do.