Some Australians, just like some Americans and some Brits, have for many years now been happily using valid second person plural pronouns. It helps in clear communication, allows succinctness of expression, and, sadly, has invariably been associated with a lack of education and low socio-economic status.

The OED identifies three varieties of the SPP. Australians, aparently along with folks from Chicago, New Jersey, parts of New York, Cincinatti, Liverpool, Northern England, and Scotland1, use the word yous(e), sometimes in a phrase like yous guys or yous all. According to Oxford, there are also yez and yiz, which are just accented variants of yous. American southerners, particularly Texans, prefer to use y'all. According to research from Texas U in 2000, though, y'all is quickly spreading northwards.

In Australia, like other places, the use of the second person plural is highly stigmatised. It is a staple of many racist jokes. It is true that many Australian Aboriginals do use the word, usually because their family's language has a second person plural pronoun and they are used to using such a word, or used to hearing their family use it. However, many non-Indigenous Australians use the SPP in conversation, despite the fact that yous is not considered a word that civilised, educated people say.

A brief history of English

Back in ye goode olde dayyes, English had a complete paradigm for the second person pronouns. In the singular, thou, thee and thy were the nominative, objective (incorporating oblique, dative and accusative) and possessive respectively. In the plural were ye, you and your.

By the middle of the seventeenth century, however, all of the singular versions of the second person pronoun had fallen out of use, and the plurals stepped up to fill the void. Ye slipped off to be sick in the bathroom after partying too hard with Chaucer and never came back.

Interestingly, tha is still used as a familiar pronoun in some parts of northern England.

Use of the second person plural pronoun

Being of neutral gender, the SPP can be used to address a group of unknown, uniform, or mixed sex.

"Where are yous guys going?"
"Do yous have tickets for the matinee performance?"
"Y'all come back now, y'hear?"
"Y'all don't seem to be from around here."

However, as pointed out by TheLibra in y'all, the SPP can be correctly used to address an individual who is a representative of a larger group, for example, an employee of an organisation or business:

"Do yous have any more of those green minty lollies with the chocolate inside?"
"Y'all need to replace the bulb in the ladies' room."

or when speaking to one person who is a member of a group:

"I wish yous were coming to the beach this afternoon."
"Can I interest y'all in savings on your long-distance phone bills?"

Though it is certainly not considered a polite form of address, neither is it particularly impolite. It is generally part of a mode of speach used in circumstances of familiarity, although it can also be used in quite formal situations when the speaker expects his audience to take it well, such as a political speach or a job interview where the audience uses the SPP themselves.

The future of the second person plural pronoun

Pronouns in English are a notoriously closed category, as the many attempts to introduce an appropriate gender neutral pronoun have demonstrated. However, many non-standard varieties of english have independently and simultaneously generated a response to the problem of the incomplete pronoun paradigm. Clearly, there is strong lexical pressure for an SPP in english. If so, which of the candidate morphemes is likely to be widely accepted?

While some linguists and armchair linguists count phrasal forms like yous guys or you lot as second person plural pronouns, no such form is likely to survive long in the highly conformist environment of a lexical paradigm. It is unlikely they would become widely accepted, and if they did, they would have to be contracted very quickly to a much shorter form. Like, for example, y'all.

Y'all is a fairly strong candidate for a universal SPP. It is short, like yous, and, like yous, is already widely spoken in certain varieties of English. Unlike with yous / youse / yez / yiz though, there are no variations in spelling, and little variation in pronounciation, so it needs very little standardisation to fit in happily.

Simple mechanics and convenience are never enough to determine the course of linguistic history, however. Social and political influences on the language are the single biggest way that lexemes and word categories change. While many American linguists have held that y'all suffers from the stigma of being from a Southern or African American dialect, its usage is spreading throughout America, first with the seemingly innocuous you all, which really doesn't take long to become y'all. Also, with the current ascendency of Southern political ethics in American national politics, it is not at all implausible to imagine that y'all could be heard echoing in the hallowed halls of the White House these days.

And who would doubt the intelligence or education of the leader of the Free World?

1 Some locality information drawn from stylee and Purvis in yous.

Proquar says educated aborigines will often use the term 'you mob'