http://images.google.com/imgres?imgurl=http://waterwatch.usgs.gov/regplots/real/real_nc_2.gif&imgrefurl=http://water.usgs.gov/waterwatch/%3Fm%3Dreal%26r%3Dnc%26w%3Dreal%252Cplot&usg=__vkTvnbBvoJv--Wb2BHENjNSJMNU=&h=450&w=550&sz=10&hl=en&start=36&um=1&tbnid=04dzXX99ouN8RM:&tbnh=109&tbnw=133&prev=/images%3Fq%3Dindex%2Bvalue%2Bmap%26ndsp%3D18%26hl%3Den%26client%3Dsafari%26rls%3Den%26sa%3DN%26start%3D18%26um%3D1
The index value plot does not plot an absolute number. All plotted values are relative to the index value. This map shows the index value for streamflow in North Carolina.