Language borders do not always reflect political borders; the tendency to correlate language with nationality is a common error[1] that seems to have arisen during the period of 19th century European expansion[2][4] (e.g., the term Anglo in Mexico and the southeastern U.S., or the term Angrez – literally, "English" – in North India). The usage of a particular language can reflect positively or negatively on its speaker depending upon the situation. For example, there is perception in the USA that only English speakers are American and only non-Americans are non-English-speakers.[1] It is suspected that this assumption began because states would have "official" languages for the purposes of book publishing and therefore for the purposes of education, so intelligence would come to be associated with speaking the language that was written.[1][4] Because of this idea, there are also often social benefits which result from being able to speak English.[3] A prime example of this is the prevalence of bilingualism near the U.S.–Mexican border,[1][3] which also indicates the porosity of the border and illustrates the difficulty of drawing a "border" around all speakers of a given language, especially because there is not usually much correlation between ethnicity and language.[3] Such common bilingualism leads to the practice of code-switching, or the changing freely between languages while speaking[1] although this trait is somewhat looked down upon[4] because those living in areas of frequent code-switching seem to develop a sort of language loyalty.[3]