Hybrid Corn and the Economics of InnovationZvi GrilichesScience, New Series, Vol. 132, No. 3422. (Jul. 29, 1960), pp. 275-280.Stable URL:http://links.jstor.org/sici?sici=0036-8075%2819600729%293%3A132%3A3422%3C275%3AHCATEO%3E2.0.CO%3B2-BScience is currently published by American Association for the Advancement of Science.Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available athttp://www.jstor.org/about/terms.html. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtainedprior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content inthe JSTOR archive only for your personal, non-commercial use.Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained athttp://www.jstor.org/journals/aaas.html.Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printedpage of such transmission.JSTOR is an independent not-for-profit organization dedicated to and preserving a digital archive of scholarly journals. Formore information regarding JSTOR, please contact [email protected]://www.jstor.orgWed Jun 13 14:05:14 2007Hybrid Corn and the Economics of Innovation Geographic differences in the use of hybrid corn are explained by differences in the profitability of that use. The idea that a cross between plants that are genetically unlike can produce a plant of greater vigor and yield than either of the parental lines dates back to Darwin and earlier. Serious research on hybrid corn, however, did not begin until the first years of this century, and the first application of research results on a substantial commercial scale was not begun until the early 1930's. During the last 25 years, the change from open pollination to hybrid seeds has spread rapidly through the Corn Belt, and from the Corn Belt to the rest of the nation. The pattern of diffusion of hybrid corn, however, has been characterized by marked geographic differences. As shown in Fig. 1, some regions began to use hybrid corn much earlier than others, and some regions, once the shift began, made the transition much more rapidly than others. For example, Iowa farmers began planting hybrid corn earlier than did Alabama farmers, and Iowa farmers increased their acre-age in hybrid corn from 10 to 90 per- cent more rapidly than did Alabama farmers. Although the explanation of area dif- ferences in the pattern of diffusion of hybrid corn constitutes the main con-tribution of the study reported here (I), it is worth drawing attention first to the striking similarity in the general pattern of diffusion of hybrid seed in the vari- ous areas. Almost everywhere the de- velopn~ent followed an S-shaped growth curve. As illustrated in Fig. 1, the rate of change is slow at first, accelerating until it reaches its peak, at approxi-mately the mid-point of development, and then slowing down again as the development approaches its final level (2).Interestingly enough, this pattern of development also applies to increases in the use of farm equipment-+om-29 JULY 1960 Zvi Griliches bines, corn pickers, pickup balers, and field forage harvesters, as illustrated in Fig. 2. Similar patterns occur in the use of new drugs by doctors and in the diffusion of other new items or ideas (3). Thus, the data on hybrid corn and other technical changes in U.S. agriculture support the general finding that the pattern of technical change is S-shaped. Although the finding that technical change follows this pattern is not very surprising or new (4),it is very useful. It allows us to summarize large bodies of data on the basis of three major characteristics (parameters) of a dif-fusion pattern: the date of beginning (origin), relative speed (slope), and final Ievel (ceiling). The interesting question then is, given this general S- shape, what determines the differences among areas in the origin, slope, and ceiling? Why were some areas ahead of others in first using hybrid corn? Why did hybrid corn spread faster in some areas than in others? Why did some areas reach higher levels of equilibrium than others? Date of Availability Although the idea of breeding hybrid corn as we know it today goes back at least to 1918, to D. F. Jones and the double cross, the dates at which superior hybrids actually became available in different areas varied widely. Hybrid corn was not a once-and-for-all innova- tion that could be adopted everywhere. Rather, it was an invention of a new method of innovating, a method of de- veloping superior strains of corn for specific localities (5). The actual proc- ess of developing superior hybrids had to be carried out separately for each locality. It is important to remember this fact before one blames, for ex-ample, the southern farmers for being slow to plant hybrid corn. Although superior hybrids became available in the Corn Belt in the early 1930's, it was only in the middle of the 1940's that good hybrids began to appear in the South. Thus, the date for a given area on which commercial quantities of su-perior hybrid seed were first produced is one of the major determinants of the development in that area. We can take the date on which an area began planting 10 percent of its corn acreage to hybrid corn as the date on which superior hybrids became avail- able to farmers in comnlercial quanti- ties. As shown in Fig. 3, different areas in the United States reached the 10-percent level on different dates. For example, this level was reached in 1936 in some parts of Iowa and in northern Illinois but was not reached until after 1948 in some parts of Alabama and Georgia. The usefulness of the 10-percent level as a measure of the com- mercial availability of hybrid corn seed is indicated by the very close cor-respondence between this and an al-ternative measure. From records of state yield tests and from other publica- tions it is possible to determine in what year hybrids first outyielded