Double clustered standard errors for panel data

Question

I have a panel data set in R (time and cross section) and would like to compute standard errors that are clustered by two dimensions, because my residuals are correlated bot

Answer 1

Arai's function can be used for clustering standard-errors. He has another version for clustering in multiple dimensions:

mcl <- function(dat,fm, cluster1, cluster2){
          attach(dat, warn.conflicts = F)
          library(sandwich);library(lmtest)
          cluster12 = paste(cluster1,cluster2, sep="")
          M1  <- length(unique(cluster1))
          M2  <- length(unique(cluster2))   
          M12 <- length(unique(cluster12))
          N   <- length(cluster1)          
          K   <- fm$rank             
          dfc1  <- (M1/(M1-1))*((N-1)/(N-K))  
          dfc2  <- (M2/(M2-1))*((N-1)/(N-K))  
          dfc12 <- (M12/(M12-1))*((N-1)/(N-K))  
          u1j   <- apply(estfun(fm), 2, function(x) tapply(x, cluster1,  sum)) 
          u2j   <- apply(estfun(fm), 2, function(x) tapply(x, cluster2,  sum)) 
          u12j  <- apply(estfun(fm), 2, function(x) tapply(x, cluster12, sum)) 
          vc1   <-  dfc1*sandwich(fm, meat=crossprod(u1j)/N )
          vc2   <-  dfc2*sandwich(fm, meat=crossprod(u2j)/N )
          vc12  <- dfc12*sandwich(fm, meat=crossprod(u12j)/N)
          vcovMCL <- vc1 + vc2 - vc12
          coeftest(fm, vcovMCL)}

For references and usage example see:

• Clustered Standard Errors in R