A measure of industry concentration and widely used in merger control.

## Usage

``concstats_hhi(x, normalized = FALSE, na.rm = TRUE)``

## Arguments

x

A non-negative numeric vector.

normalized

Logical. Argument specifying whether or not a normalized value is required. Ranges from 0, 1 and often used for comparison over time. Must be either `TRUE` or `FALSE`. The default is `FALSE`.

na.rm

A logical vector that indicates whether `NA` values should be excluded or not. Must be either `TRUE` or `FALSE`. The default is `TRUE`. If set to `FALSE` the computation yields `NA` if `NA` values are present.

## Value

A single numeric measure in decimal form.

## Details

`concstats_hhi` calculates the widely used Herfindahl-Hirschman Index (Herfindahl, 1950 and Hirschman, 1945). The index is calculated by squaring the market share of each firm competing in the market and then summing the resulting numbers.

## References

Herfindahl, O. C. (1950), "Concentration in the steel industry" (PhD thesis), Columbia University.

Hirschman, A. O. (1945), "National power and structure of foreign trade". Berkeley, CA: University of California Press.

Other Competition/Concentration measures: `concstats_all_comp()`, `concstats_comp()`, `concstats_dom()`, `concstats_hhi_d()`, `concstats_hhi_min()`, `concstats_sten()`

## Examples

``````# a vector of market shares
x <- c(0.35, 0.4, 0.05, 0.1, 0.06, 0.04)
concstats_hhi(x)
#> [1] 0.3002
# a vector with NA values
x <- c(0.4, 0.2, 0.25, 0.1, 0.05, NA)
concstats_hhi(x, na.rm = FALSE)
#> [1] NA

``````