Shock summary: effective number of shocks and exposure concentration

Reports the Borusyak-Hull-Jaravel (2022) exposure-concentration diagnostics for the shocks route: the average exposure (importance) weight of each shock, its Herfindahl index, and the *effective number of shocks* \(1/\sum_n \bar s_n^2\). Few effective shocks undermine the large-n asymptotics that justify the shocks-exogeneity approach.

Usage

ssb_shock_summary(design)

Arguments

design

An [ssb_design()] object.

Value

A list with `effective_shocks`, `hhi`, `n_shocks`, and a `data.frame` `weights` of per-shock importance weights (descending). Class `ssb_shocks`.

Examples

sim <- ssb_simulate(n_loc = 80, n_sec = 10, seed = 1)
d <- ssb_design(sim$data, sim$shares, sim$shocks, exogenous = "shift")
ssb_shock_summary(d)
#> <ssBartik shock summary>
#>   shocks (cells)     : 10
#>   effective shocks   : 9.8  (HHI 0.102)
#>   largest exposure   : 0.122 (3)