The persistence of Guarani is, contrary to popular belief, not exclusively, or even primarily, due to the influence of the Jesuits in Paraguay.Jesuit reductions.
While Guarani was the only language spoken in the expansive missionary territories, Paraguayan Guarani has its roots outside of the
Modern scholarship has shown that Guarani was always the primary language of colonial Paraguay, both inside and outside the reductions. Following the expulsion of the Jesuits in the 18th century, the residents of the reductions gradually migrated north and west towards Asunción, a demographic shift that brought about a decidedly one-sided shift away from the Jesuit dialect that the missionaries had curated in the southern and eastern territories of the colony.
By and large, the Guarani of the Jesuits shied away from direct phonological loans from Spanish. Instead, the missionaries relied on the agglutinative nature of the language to formulate calque terms from native morphemes. This process often led the Jesuits to employ complicated, highly synthetic terms to convey Western concepts. By contrast, the Guarani spoken outside of the missions was characterized by a free, unregulated flow of Hispanicisms; frequently, Spanish words and phrases were simply incorporated into Guarani with minimal phonological adaptation.
A good example of this phenomenon is found in the word "communion". The Jesuits, using their agglutinative strategy, rendered this word "Tupârahava", a calque based on the word "Tupâ", meaning God. In modern Paraguayan Guarani, the same word is rendered "komuño".
Following the out-migration from the reductions, these two distinct dialects of Guarani came into extensive contact for the first time. The vast majority of speakers abandoned the less-colloquial, highly regulated Jesuit variant in favor of the variety that evolved from actual language usage by speakers in Paraguay. This contemporary form of spoken Guaraní is known as Jopará, meaning "mixture" in Guarani.
A government sign in Asunción
, bilingual in Guaraní and Spanish
Paraguayan Guarani has been used throughout Paraguayan history as a symbol of nationalistic pride. Populist dictators such as José Gaspar Rodríguez de Francia and Alfredo Stroessner used the language to appeal to common Paraguayans, and upon the advent of Paraguayan democracy in 1992, Guarani was enshrined in the new constitution as a co-equal language along with Spanish.  Jopara, the mixture of Spanish and Guarani, is spoken by an estimated 90% of the population of Paraguay. Code-switching between the two languages takes place on a spectrum where more Spanish is used for official and business-related matters, whereas more Guarani is used in art and in everyday life.
Guarani is also an official language of Bolivia and of the Argentine province of Misiones.