I know it should be blindingly obvious, but the size of construction projects is directly related to their lead time. Something like Crossrail takes twenty years before the first 360 hits the ground. Schemes under £5m can generally start fairly rapidly, and £5m - £10m schemes are the bread and butter of the industry, with skills, plant, materials and construction teams ready 'off the shelf'. The classic value release curve for a scheme is remarkably similar to a tidal curve, and it's the fast-spending middle bit that drives the ONS construction output figures.The lag means that Q1 2012 figures reflect decisions made two or three years ago.
Unlike public 'consumption' spending, which is mainly employing new people on permanent contracts, 'capital' can be turned on and off like a tap. If you pick the right schemes, the economic benefit can hit the economy during the term of a single Parliament. And you'd imagine that this would be attractive to politicians - but no. Even when they decide that investment spending - spending that leaves a tangible asset as well as its economic effect - is a good thing, they prefer to pick the massive, prestige, big-dicked schemes that can't possibly deliver any economic benefit during their own time in office. Sure, they provide plenty of work for construction professionals, lawyers and office staff in the early years, but none where it counts - labour, materials, plant, transport, waste - and indirectly in accommodation and services. Services aren't just the bacon sarnie vans that make a mint adjacent to a construction site; the construction phase of the Melbourne Olympics attracted some 10,000 prostitutes to service the workforce.