Housing Affordability Index

Entry type: Single project

Country/area: Belgium

Publishing organisation: De Tijd

Organisation size: Big

Publication date: 2022-06-09

Language: Dutch

Authors: Olaf Verhaeghe, Thomas Segers, Raphael Cockx, Thomas Roelens


De Tijd’s Data & Interactive team publishes original news stories supported by in-depth data analysis. Our team uses its diverse skills to collect, analyze and visualize data in order to discover new trends, interesting patterns and surprising outliers. Our publications are supported by insightful graphics that make complex ideas understandable. Through interactive news applications, we guide readers step-by-step through the story and provide personalized information.

Project description:

De Tijd developed an innovative tool to track the affordability of housing.The index was built from three parameters: the price of real estate, the income of the buyer, and the interest rate offered by banks. The index shows that buyers are spending an increasing proportion of their income on financing their homes. In two thirds of the municipalities, the price has risen so much that an average family needs more than a third of its income to pay off the mortgage. An interactive explainer was developed for all municipalities, allowing readers to inform themselves about the affordability in their area.

Impact reached:

The index and tool revealed that in two-thirds of municipalities, a median income is no longer sufficient to pay off a typical house. The explainer and subsequent news articles reached over 100,000 readers. Through the combination of news and background information, the tool has gained a significant position in De Tijd’s real estate reporting.

Techniques/technologies used:

The data-analysis was done in R based on an adaption of the methodology by the American National Association of Realtors.

For the latest real estate prices, we rely on the Notary Barometer of the Federation of Notaries. The average price is displayed every quarter and per municipality. Quarters with insufficient transactions are extrapolated and displayed with a dotted line.

For family incomes, we rely on figures from Statbel, the Belgian statistics bureau. We only take into account joint tax returns and use the median taxable income for each city or municipality. The income data for 2020, 2021, and 2022 are calculated based on the latest tax returns from 2019 and corrected for inflation.

The interest rates come from the interest rate barometer of Immotheker-Finotheker. To determine the interest rate, we assume a fixed rate with a term of 20 years and a down payment of 15 percent of the purchase price. A quarterly average is calculated every quarter.

The interactive webpages were built using Vue.js for the framework and D3.JS for the interactive graphs.

Context about the project:

A customized web page was created for all 300 Flemish cities and municipalities. Texts and graphics were adapted based on detailed municipal data. The interface elements were also customized to allow readers to navigate swiftly to the results for neighboring and comparable municipalities.

What can other journalists learn from this project?

This project helped us to strengthen our real estate reporting, provide additional insights into the affordability of homes and simulate the effects of interest rate increases and salary changes, in addition to tracking the evolution of housing prices.

Project links: