Socioeconomic characteristics and time dependency In the application, all the socioe- conomic characterics are categorical variables. Consider the Q categorical variables W ( q ) h,t , q = 1 , . . . , Q, with m$_{q}$ modalities, and fix the m th q modality as the reference modality, then the socioe- conomic effect term in (2.2) and (2.3) is where γ$_{q,m}$ is the effect of the m th modality of the socioeconomic variable q. Similarly, time is only measured by weekly counts throughout the year so that the time effect in (2.2) and (2.3) is simply where α$_{τ}$ is the effect of week τ and τ$_{R}$ is the reference week. Error specification The error at the individual level ε$_{i,h,t}$ is assumed to be Gaussian with zero mean, and the variance-covariance structure is such that where ρ measures the dependence between individuals within the same household. w$_{h,t}$γ = Q ∑ q =1 m$_{q}$ − 1 ∑ m =1 γ$_{q,m}$ $^{1l}$n W ( q ) $_{h,t}$= m o , δ$_{t}$α = T ∑ τ =1 = τ$_{R}$ α$_{τ}$ 1l$_{{}$$_{τ}$$_{=}$$_{t}$$_{}}$ , cov ( ε$_{i,h,t}$, ε$_{i}$ $^{′}$,h$^{′}$,t′ ) = 0 , cov ( ε$_{i,h,t}$, ε$_{i}$ ′ $_{,h,t}$) = ρσ 2 $_{ε}$, cov ( ε$_{i,h,t}$, ε$_{i}$ $^{′}$,h,t′ ) = 0 . 10 • households are independent, i.e. ∀ i, i $^{′}$, t, t′ and ∀ h = h ′ • members of the same household are dependent, that is for ∀ h, t and i = i $^{′}$, • there is no time dependence, that is ∀ i, i ′ and ∀ t = t ′