A new analysis of Auckland's growth suggests population forecasts may be too high, and the ability of the city to provide housing may fall dramatically short.
The report has been eagerly awaited, dealing with two of the biggest questions confronting Auckland, but there's disagreement within the group of experts that produced it.
The report is for the independent panel considering Auckland's proposed development blueprint, the Unitary Plan.
The panel assembled 15 experts from within Auckland Council and the private sector, including planners, developers and demographers.
Its job was to apply "real world" criteria to the council's previous forecasts, on likely population growth, and how many new dwellings would really be built under the plan's push for greater intensification.
On population growth, the council forecasts 1 million additional residents by 2041. The group believes it may be only 700,000 - 800,000.
However, some within the group consider that figure may be too conservative.
There was general agreement that the council's aim to have 60-70 percent of growth within the urban limits was not achievable.
But in trying to estimate, using "real world" factors, how many homes and in what style might be built by 2041, there was less agreement.
Three different streams of work were blended into one model produced by the council's own research unit RIMU and dubbed ACDC15.
The ACDC15 figures show a theoretical 565,000 new dwellings could be built under the rules proposed in the plan at present.
When it produced a figure of how many homes could "feasibly" be built, the figure was on 64,420, just 26 percent of the theoretical number.
This was arrived at by applying a lengthy list of factors such as the expected price of land, construction, future preferences for housing styles, and even the likelihood that neighbours would agree to sell their properties to create larger development sites.
One significant variable is how many homes can be built by Housing New Zealand. The state-owned company intends to build 39,000 additional dwellings by 2041, but under the current provisions in the plan, could build only 19,000.
The report repeatedly refers to disagreement among the 15 members, and it includes appendices showing the differing views of individual members.
One told Radio New Zealand the group had become increasingly fractious.
The report still describes its findings as valuable, and it will be available as a resource to all submitters, as the panel approaches critical areas such as intensification, and the placing of the urban boundary.