The age-old debate over what to call a soft drink appears to be, well, a pop-up. Thirty-eight percent of Americans refer to effervescent beverages as â€œsodaâ€? and another 38 percent call it â€œpop,â€? according to an informal Internet poll of more than 100,000 individuals. There is also a sizable minority (19 percent) who refer to carbonated beverages merely as â€œCokeâ€? â€” even when it's a Pepsi. The ongoing survey, which began eight years ago as a college project by students enrolled at the California Institute of Technology in Pasadena, and at Lewis & Clark College in Portland, Ore., asks visitors to the site (www.ugcs.caltech.edu/~almccon/pop_soda/) to enter the ZIP code for the town they grew up in and the term they use for soft drinks. Respondents' votes are then placed on a map as colored dots. Researchers have found wide linguistic variation by region. For instance, â€œCokeâ€? is most often used in the South, â€œpopâ€? in the Midwest and â€œsodaâ€? in the Northeast and Southwest. Interestingly, Missouri and Wisconsin (the St. Louis and Milwaukee areas, in particular) are islands of â€œsodaâ€? afloat in a sea of Midwestern â€œpop.â€?