How did Belgium change from a unitary state into a federal state?

Prior to 1970, Belgium functioned as a unitary state. The transition to a federal state was driven by decades of mounting tensions between the country’s major ethnolinguistic groups, exacerbated by growing economic disparities between the Flemish and Walloon regions.12

As the Flemish economy prospered through foreign investment and the Walloon region struggled with aging heavy industry, political dissatisfaction with the unitary system intensified. Flemings grew frustrated with subsidizing the Walloon economy, while Walloons feared political domination by the more numerous Flemish population. These linguistic and economic tensions eventually caused the nation's traditional political parties to split along linguistic lines, complicating the decision-making process.123

To address these conflicts, Belgium underwent a series of constitutional reforms throughout the 1970s, 1980s, and 1990s. This process dismantled the unitary structure, culminating in the St. Michael’s Agreement of 1992. The resulting federal framework was approved by parliament in 1993 and enshrined in a new constitution in 1994, establishing a system where national authorities share power with regional and community executive and legislative bodies.2