Are Dutch and French languages miscible?

TL;DR

This study uses a mathematical sociolinguistic model to analyze historical data on French and Dutch in Brussels, assessing whether both languages can coexist or if one will dominate or extinguish the other.

Contribution

It introduces a sociolinguistic dynamic model fitted to historical data to evaluate language coexistence versus dominance in Brussels.

Findings

Data suggests limited long-term coexistence of Dutch and French.

French tends to dominate or lead to the extinction of Dutch.

Model indicates non-coexistence is more likely than stable bilingualism.

Abstract

We study the stability of the cohabitation of French and Dutch in the Brussels-capital region (Belgium). To this aim, we use available time series of fractions of speakers of monolinguals of both tongues as well as the fractions of bilinguals. The time series span a period from the mid-XIX century until 1947, year of the last accepted linguistic census. During this period, French penetrated the Dutch-vernacular region of Brussels and started a language shift that lasts to this day. The available time series are analyzed with a mathematical model of sociolinguistic dynamics that accounts for cohabitation of languages along bilingualism. Our equations are compatible with long-term coexistence of both languages, or with one tongue taking over and extinguishing the other. A series of model parameters (which we constrain by fitting our equations to the data) determine which long-term trajectory (cohabitation or extinction) would be followed. This allows us to estimate whether the empirical data are compatible with a coexistence of Dutch and French -- in physics terms, whether both tongues are {\em miscible}. Our results tilt towards non-coexistence, or coexistence with a starkly-dominated, minority language. The costs of attempting to sustain such sociolinguistic system are discussed.