The updated calculation tool (year 2024) is described in the following points.

The calculation tool is the central tool for implementing the Bonn building land model, taking into account the appropriateness to be observed in accordance with Section 11 (2) BauGB. All assumptions of the building land model are stored in the calculation tool so that it can produce results with just a few inputs of property parameters. It is used to calculate the total yield to be expected from a residential construction project at the location of a construction area on a flat-rate basis. The calculation tool is important for the application of the Bonn Building Land Model in two respects. Firstly, the yield calculation carried out with it serves as the basis for the appropriateness test according to the yield method, and secondly, the yield calculation is used to determine the economic disadvantage of the mandatory quotas for subsidized housing construction.

The calculation assumptions are regularly updated from April of each year. This specific period was selected in order to be able to carry out an update as soon as possible after the publication of the City of Bonn's property market report, which contains information relevant to the Bonn building land model (e.g. on the property interest rate, gross yield factor, etc.).

In the course of updating the calculation tool for carrying out the appropriateness tests associated with the application of the Bonn Building Land Model, the following calculation assumptions were finally adjusted in June 2024:

The following calculation assumptions remain unchanged, as no or no fundamental changes were made in the past year:

To illustrate the effects of updating the basic assumptions of the calculation tool, the update report includes appropriateness tests with the previous versions V1.1.0 (2019), V2.1.0 (2020), V3.1.0 (2021), V4.1.0 (2022), V5.1.0 and the updated version V6.0.0 (2024) of the calculation tool. The appropriateness tests are carried out as examples for the "simple/medium", "good" and "very good" residential locations anchored in the Bonn building land model and on the basis of real urban development designs and their corresponding key figures. This is done against the background that the residential location of a residential construction project is decisive for the allocation to a rent for privately financed residential construction and thus has an influence on the calculation of the land value of the residential construction areas and the amount of the economic disadvantage of subsidized residential construction.
The charts and explanations show the changes in the results of the appropriateness tests induced by the annually adjusted calculation assumptions with an appropriateness limit of 30% of the expected yield from the respective development project. This value roughly comprises the expected yield of a residential construction project after 20 years (present value) and the resulting conclusions. Among other things for the appropriateness limit, the benefits to be agreed and the amount of the economic disadvantage resulting from the mandatory realization of the proportion of publicly subsidized housing specified by the Bonn building land model (depending on the gross floor area residential 40%, for the vast majority of development projects 50% of the total gross floor area residential). For the updated version 6.0.0 of the calculation tool for the Bonn building land model, a commitment period of 30 years for publicly subsidized housing construction has again been set as the calculation assumption this year in accordance with the housing subsidy regulations of the state of North Rhine-Westphalia; the cash flow (rental income less management and financing costs) continues to be based on an assessment period of 20 years.

Information on the development plan procedure:

Information on the development plan procedure:

Information on the development plan procedure:

The dynamic development of the housing industry in Bonn was already reflected in the calculation tool updates of previous years, and this year's update also shows that the development momentum of recent years is continuing. It is reflected in the appropriateness test in the Bonn building land model by adjusting various assumptions for the calculation tool and continues to be reflected primarily in ongoing increases in construction and financing costs. As in previous years, these cost increases are having a correspondingly greater impact on the realization of new residential construction projects on the Bonn housing market.
The yield expected in Chapter 2 (see 2.1. to 2.3.) for the respective theoretical development projects after 20 years is lower compared to the previous year's figures on the basis of the updated calculation tool assumptions. Among other things, this is due to the continued rise in construction costs outlined above, which minimizes the corresponding return expectations. In this context, the transfer of the increase in construction costs to the development of the production costs of daycare places, which was again carried out analogously in the context of this year's calculation assumption update, also continues to have a potentially earnings-reducing effect.
On the other hand, the housing subsidy regulations (WFB) of the state of North Rhine-Westphalia, which have been improved once again for the 2024 funding year compared to the previous year 2023 and more significantly than in any previous update context, significantly reduce the financial disadvantage of publicly subsidized housing construction compared to the privately financed market segment in all three calculation examples. In some cases, the improvement in the WFB is so significant that, among other things, this reverses the signs of the economic disadvantage of the mandatory realization of publicly subsidized housing construction, particularly for the calculation examples in simple/medium and good residential locations, to an advantage (see 2.1. to 2.2.). As in the context of the previous update from 2023, the persistently high interest rate level for residential construction loans has a significant impact on the burden on project developers in residential construction in the reference period relevant for this update (April 2023 to March 2024). Although the pace of price increases has slowed somewhat compared to the previous year, the assumed interest rate has continued to rise.
All in all, the developments described above have different effects on the calculation examples created using the updated calculation tool version V6.0.0. Compared to the previous year, however, the appropriateness limit of 30% of the assumed return on a development project set in the Bonn building land model is only exceeded for the calculation example in very good residential locations, i.e. for development projects in areas with correspondingly high land prices and simultaneously high income prospects. In these development areas, it is foreseeable that potential developers will no longer have to contribute fully to the production costs of the need for daycare places resulting from the construction of new housing. In contrast to the previous year, however, there is no longer a reduction in the proportion of publicly subsidized housing to be realized in any of the calculation examples via the updated calculation assumptions for the appropriateness test.
In particular, the comprehensibility of the effects that have resulted from the significant improvement in the housing subsidy regulations of the state of North Rhine-Westphalia for project developers also shows in the context of this year's update that the calculation tool of the Bonn building land model and thus also the building land model itself react to changing market conditions. In challenging times, not only in terms of Bonn's housing market structure, it appears to be able to continue to enable the most transparent balance possible between the public and private sector interests of all housing developers for a sustainable design of Bonn's housing market.