This paper addresses a recent language change in U.S. The surprising aspect of this change is that it went unnoticed while it occurred among younger speakers in different parts of the country while older speakers continued to use the older form. The change was one affecting replacement in only a small part of the lexicon: that of by accident to on accident.
It is commonly acknowledged that variation in the use of prepositions among regional and social varieties is quite common (e.g. different than vs different to vs different from, quarter to vs quarter till vs quarter of, on line vs in line, to name a few). Wolfram & Schilling-Estes (1998, 343-44) have noted that often speakers are completely unaware that the preposition they are using in a given construction is not found in all English varieties. Such is the case with speakers of the innovative on accident. How then, did the form take hold in such disparate areas as Terre Haute, Indiana, Farmington Hills, Michigan, Irvine, California, and McRae, Georgia? These four communities are not just geographically far apart; they are also quite different in terms of size, economics, social classes, and ethnic diversity. Yet, this paper will report on a study which demonstrates that the same change from by accident to on accident took place within the same age groups during the same period of time in all four places.
The paper will also show that while by accident is still more common overall than on accident, and while older speakers still use by accident and often do not accept on accident, among younger speakers of U.S. English, on accident is common and, in fact, has equal acceptance with by accident. In many cases, younger speakers are even unaware of the existence of by accident.
Interestingly, on accident seems to have no social significance for speakers who use it. In contrast, there is some evidence that on accident does have social significance for some speakers who use by accident, but this is no means general: many by accident speakers do not notice that other people say on accident.
Why on accident spread throughout the U.S. is not clear. Obviously, on purpose may have played a role in supplying an analogical form (I didn't break the window on purpose; I broke it on accident), but why this changed occurred at the time that it did and in the direction that it did is even less clear. Based on the correlation of on accident usage with age, it is likely that on accident usage will continue to grow and replace by accident as the common U.S. phrase in the future.
Wolfram, Walt, and Natalie Schilling-Estes. 1998. American English. Malden, Massachusetts: Blackwell Publishers.