Land Price vs Height

Take any central business district, assessor's roll in one hand and building heights in the other, and plot them. The cloud of points rises to the right. That slope is the vertical push measured.

The economic height

A developer adds floors while the next floor earns more than it costs. Each floor above the first few costs more than the one below: more structure to carry it, more elevator to serve it, more bracing against wind, more time on the crane. Rent per square foot, meanwhile, rises with the view and the address up to a point and then flattens. Where the rising cost curve crosses the flattening revenue curve is the economic height. A high land price shifts the whole calculation: the developer is spreading a large fixed cost (the lot) over more floors, so the crossing moves up.

The same curve, different scales

Chicago's Loop, Manhattan below 59th, Hong Kong Central, Nassau's Bay Street — one curve, four scales. Where the ground is $50 a square foot the crossing is four stories; where it is $3,000 the crossing is sixty. The shape is the same because the arithmetic is the same.

What moves the curve

A transit station moves access, which moves land price, which moves height — usually with a lag of a development cycle. A height limit caps the curve and pushes the pressure outward (Washington) or into the ground (Paris La Défense outside the limit). A land-value tax raises the cost of holding low-density land at the centre and pushes height up. Cheap credit brings the crossing forward; expensive credit pushes it back, sometimes leaving a stub.

Measuring it

The surveyor's plat gives the square feet of the lot; the assessor's roll gives its price; the building department gives the height; the GIS technician joins the three on a map. That is a program at this school — GIS / Surveying / Drone Operations — and the live GIS table in Gallery G9 draws this chart for the region every time a visitor asks it to.

Why it belongs in a trade school

Because the students of this school are the people who will stand at the top of the curve, tying rebar. A welder who understands why the tower is sixty stories rather than six understands the client.