I found this on another list, and believe it will help you understand the GV better. "For the researcher then, a distribution study of any particular surname can be used to prioritize research. It can also be useful as general background information for a family history, showing how common or scarce, widespread or restricted, the name is in Ireland. Sometimes a surname distribution study will yield some real surprises. For example, a recent study of the surname Huntley failed to locate even one citation for that spelling in Griffith's! Two variant spellings were found, but only one citation to each - a Huntly in County Kilkenny and a Hundley in County Sligo. If ones Huntley ancestor left Ireland after Griffith's then one of these would likely be the desired family. When the distribution is this small however, it is difficult to judge where the family may have come from if they left Ireland prior to Griffith's Valuation. Perhaps the whole family left an area, leaving no one of that surname. Even in this case though, some useful information has been garnered--you know that if you find a record of the correct name and time period for your Huntley ancestor in Ireland, it is very likely the correct person, rather than someone coincidentally of the same name. There are two general types of distribution studies possible using Griffith's index. One is a study showing the frequency with which a surname is cited in each of Ireland's 32 counties. This gives a good overview, and helps determine if the name is localized or widespread. The second type of distribution shows how often the name is cited in each parish. There are about 2500 parishes in Ireland, so it is usually not practical to do this type of study for the entire country. If however, the county of origin is known for an ancestor, this kind of study, for one county, can be very useful. A parish by parish distribution study can be especially useful when you know both names for a couple who were married prior to emigrating. Except among the wealthy, most Irish found their mates nearby--often from the same parish or an adjoining one. Comparing the distributions for two names within a county will often limit the area you need to search to just one or two parishes (depending how common the names of course). Once you know where to search, local parish records can be consulted. Distribution studies are not a panacea, but wisely used they may save you a lot of work. When used as general background information, they are always interesting. Now that studies are available at minimal cost, you might want to have one done even if you already know the exact place of origin for your ancestor -- knowing where other members of the family lived can help fill in the "big picture" for you. Remember that distribution studies will not give you the exact place of origin for your ancestors, they will only tell you which places are most likely, so that you can prioritize further research."