On the other hand, a number of studies reviewed in Fuson (1990) indicated that American children, ranging from second to fifth grade, frequently lack both conceptual and procedural knowledge of multidigit addition and subtraction. Lack of conceptual understanding was evident in findings that almost half of third graders incorrectly identified the place value of digits within multidigit numbers (Kouba, Carpenter & Swafford, 1989; Labinowicz, 1985), and in findings that most second through fifth graders could not demonstrate or explain ten-for-one trading with concrete representations (Ross, 1986).