Monthly skill share panel from posting-level incidence — compute_share

Builds the share panel \(s_{k,t} = x_{k,t} / n_t\), where \(x_{k,t}\) is the number of postings of period \(t\) that mention skill \(k\) and \(n_t\) is the number of postings of period \(t\) with at least one skill. When group_cols are given (e.g. a profession code) counts and denominators are computed within each group.

Usage

compute_share_panel(
  incidence,
  id_col = "general_id",
  time_col = "mese_idx",
  skill_col = "skill_id",
  group_cols = NULL,
  fill_zero = TRUE
)

Arguments

incidence: A data.frame/data.table with one row per posting and skill (duplicates are removed). Must contain id_col, time_col, skill_col and any group_cols. Each posting must belong to a single period and group.
id_col: Posting identifier column. Default "general_id".
time_col: Period column (typically an integer month index). Default "mese_idx".
skill_col: Skill identifier column. Default "skill_id".
group_cols: Optional character vector of grouping columns (e.g. "cp4"). Default NULL (global panel).
fill_zero: Logical. When TRUE (default) every group-skill pair observed at least once gets a row for every period in which its group has postings, with x = 0 where the skill is absent.

Value

A data.table with columns group_cols, skill_col, time_col, x (postings with the skill), n (postings with at least one skill) and quota (x / n), keyed by the first three.

Examples

inc <- data.table::data.table(
  general_id = c(1, 1, 2, 3, 3, 4),
  mese_idx = c(1, 1, 1, 2, 2, 2),
  skill_id = c("a", "b", "a", "a", "c", "b")
)
compute_share_panel(inc)
#> Key: <skill_id, mese_idx>
#>    skill_id mese_idx     x     n quota
#>      <char>    <num> <int> <int> <num>
#> 1:        a        1     2     2   1.0
#> 2:        a        2     1     2   0.5
#> 3:        b        1     1     2   0.5
#> 4:        b        2     1     2   0.5
#> 5:        c        1     0     2   0.0
#> 6:        c        2     1     2   0.5