Rural community weather-index advisory subscription costs and smallholder replanting decisions in Zambian wards: an instrumental-variable analysis of extension-message exposure

Smallholder replanting decisions in Zambian wards are shaped by the cost of subscribing to community weather-index advisory services, yet the causal direction of the relationship between subscription cost and replanting behaviour remains poorly identified because unobserved household characteristics jointly determine both. The framework specifies the conditions under which cost-based instruments satisfy relevance and exclusion restrictions, distinguishes between message exposure and message uptake, and formalises the replanting decision as a threshold response to expected net returns under weather uncertainty. The contribution is a bounded identification argument that clarifies what can and cannot be learned about advisory pricing and replanting behaviour from ward-level observational data, and it specifies the data requirements and falsification tests that would permit credible estimation. The framework is intended for application to household survey data from Zambian wards and provides a template for comparable analyses of agricultural advisory pricing in rural African settings.