The irrigated areas of Punjab, Pakistan, were the locus of the Green Revolution in wheat, where all varieties grown today
are modern. Despite that transformation, many rural Pakistanis still suffer from malnutrition, including zinc deficiency.
Zinc-biofortified wheat varieties are one approach for alleviating this problem among poor farming households who do
not have access to enriched food products. To promote new varieties effectively, decision makers need to understand
why some varieties become more popular than others, especially for this target group.
This paper applies duration analysis to identify the factors that shorten the time until a farmer replaces one modern
variety with another, and tests hypotheses concerning two salient themes of the Green Revolution: farm size differences
and the role of information in farmer-to-farmer seed diffusion. Findings indicate that the time span between changing
varieties averages only four years, but is shorter on larger farms. Factors that speed variety change also differ by farm
size. Extension and media sources of information are significant among larger farmers relative to social information,
which is more important among marginal farmers. Traits related to consumption quality speed variety change among
smaller-scale farmers, who both sell and consume their wheat. Higher yields drive variety change among the most
subsistence-oriented, marginal farmers.