All individuals in a social system do not adopt an innovation at the same time. Rather, they adopt in an ordered time sequence, and they may be classified into adopter categories on the basis of when they first begin using a new idea. In technology transfer programme, it is of great practical utility for the extension workers to identify the individuals who are likely to adopt innovations early and who may lag behind.
The adoption of an innovation over time follows a normal, bell-shaped curve when plotted over time on frequency basis. If the cumulative number of adopters is plotted, it results in an S-shaped curve. The S-shaped curve rises slowly at first when there are few adopters in a time period, accelerate to a maximum when about half of the individuals in the system have adopted and then increases at a gradually slower rate as the few remaining individuals finally adopt. The S-shaped curve is like that of a ‘learning curve’ as propounded by the psychologists. Each adoption in the social system is in a sense equivalent to a learning trial by an individual.

S- Shaped cumulative curve
Percentage of adopters

Bell shaped curve-Adopter categories on the basis of Innovativeness

           Both of these curves are for the same data, the adoption of an innovation over time by the members of a social system. But the bell-shaped curve shows these data in terms of the number of individuals adopting each year, whereas the S-shaped curve shows these data on cumulative basis. The distribution of adopters over time closely approaches normality, and may be explained by the statistical concept of normal curve.
The distribution of the adopters may be partitioned into five adopter categories by using the mean and standard deviation. The area lying to the left of the mean time of adoption minus two standard deviations includes 2.5 per cent of the individuals who are the first to adopt an innovation and are known as innovators. The next 13.5 per cent between the mean minus one standard deviation and the mean minus two standard deviations to adopt the new idea are called as early adopters. The next 34 per cent of the adopters between the mean date of adoption and minus one standard deviation are known as early majority. Between the mean and one standard deviation to the right of the mean are located the next 34 per cent to adopt the new idea, the late majority. The last 16 per cent to the right of mean plus one standard deviation are the last to adopt the innovation the laggards.

Innovators: Venturesome
Observers have noted that venturesome is almost a fascination with innovators. They are eager to try new ideas. This interest leads them out of a local circle of peers and into more cosmopolite social relationships. Communication patterns and friendships among a group of innovators are common, even though the geographical distance between the innovators may be great. Being an innovator has several prerequisites. He desires the hazardous, the rash, the daring, and the risky. The innovator also must be willing to accept an occasional setback when one of the new ideas he adopts proves unsuccessful. These are the first people to adopt a new idea, much ahead of other people. They are very few in numbers, probably not more than one or two in a community
The innovators have friendship networks that extend outside of their local system they are oriented to develop well contact with the research station and high level extension functionaries.

Early Adopter: Respectable
They are localite and are a more integrated part of the community. Because early adopters are not too far ahead, the average members of the community can comprehend their activities relating to adoption of the innovation. They have more opinion leadership and potential adopters look to them for advice and information about the innovation. They try to maintain adoption leadership to keep up their prestige in the community.
Early adopters are literate, have large size enterprise, high income, more participative and maintain good contact with cosmopolite sources of information. They do not test untried ideas, but quickest to use tried ideas in their own situations.

Early Majority: Deliberate (Local Adoption Leaders)
They adopt new ideas just before the average members of the community. They are neither very early nor relatively late to adopt an innovation. They are neither very early nor relatively late to adopt an innovation. They are deliberate and take longer time to make the decision to adopt, in comparison to the innovators and early adopters. They do not hold leadership position in adoption, but actively participate in extension programmes like training, demonstration, farmers day, study tour etc. they are slightly above average in education. Social and economic status, and experience about the enterprise. Because of their limited resources, they cannot take hasty or poor decisions.
They have less contact with the cosmopolite sources of information. They are active localities and associate mainly with the people of their own community. They are the ‘neighbours and friends’ from whom majority of the members of the community seek information about innovations.

Late majority:
They are cautious and skeptical, and adopt new ideas just after the average members of the community. They adopt mainly because people have already adopted the innovation and are getting the benefit out of it.
They have low level of education, low level of participation and depend mostly on localite sources of information.

Laggards:
Laggards are traditional and the last to adopt an innovation. By the time laggards finally adopt an innovation, it may already have been superseded by a more recent idea which the innovators are already using.
They are most localite and primarily interact with those who have traditional values.    They tend to be frankly suspicious of innovations, innovators and change agents. A fast moving world is shocking to them and they find it difficult to adjust with it. They do not have opinion leadership and is almost a forgotten mass of people in the community. They have little or no education, least participant and hardly any contact with the outside world.
These people are likely belong to the backward classes, may be working as share- croppers and agricultural labourers, with very little land of their own. They are generally resource-poor people with little surplus to invest in their production enterprise. They generally live in areas having least urban influence and, socially and economically the most disadvantaged.