A severity-weighted crime index

Offence rates combined into one index, unweighted (the sum of rates) and weighted by each offence's severity (for example its mean statutory sentence), per unit and period.

Usage

sevidx(data, unit, time, offence, count, w, pop = NULL, per = 1e+05)

Arguments

data

A data frame, one row per unit, period and offence.

unit, time, offence, count

Column names.

w

Named weights, one per offence counted.

pop

Optional column name of the population; without it count is taken as a rate already.

per

Rate base (default 100000).

Value

A data frame of class rmbl_severity: unit, time, unweighted, weighted; attribute weights.

Details

With \(r_{k}\) the rate of offence \(k\) per per residents and \(w_k\) its weight, the indices are \(\sum_k r_k\) and \(\sum_k w_k r_k\). Mean statutory sentence lengths are one choice of weight (as in Acosta, Mejia and Zorro Medina 2023); sentencing guidelines are another (the Cambridge Crime Harm Index, Sherman, Neyroud and Neyroud 2016). The weights are the analyst's to state and defend: the index records them. A unit-period missing an offence that has a weight gets NA, never a partial sum.

References

Sherman L, Neyroud PW, Neyroud E (2016). The Cambridge Crime Harm Index: measuring total harm from crime based on sentencing guidelines. Policing 10(3):171-183. doi:10.1093/police/paw003

Applied with weights from the Colombian Penal Code: Acosta, Mejia and Zorro Medina (2023), see plndid.

Examples

d <- data.frame(
  city = rep(c("A", "B"), each = 3),
  year = 2024,
  offence = rep(c("homicide", "robbery", "burglary"), 2),
  n = c(5, 120, 300, 2, 90, 410),
  pop = rep(c(250000, 180000), each = 3)
)
sevidx(
  d,
  "city",
  "year",
  "offence",
  "n",
  w = c(homicide = 25, robbery = 8, burglary = 4),
  pop = "pop"
)
#> ╭── Severity-weighted index ──────────────────────────────────────────────╮
#> │   Rows               2                                                  │
#> │   Units              2                                                  │
#> │   Periods            1                                                  │
#> │   Offences weighted  3                                                  │
#> │                                                                         │
#> │   Index                                                                 │
#> │   unit   time  unweighted  weighted                                     │
#> │   ----  -----  ----------  --------                                     │
#> │   A     2,024       170.0       914                                     │
#> │   B     2,024       278.9     1,339                                     │
#> │                                                                         │
#> │   Weights                                                               │
#> │   offence   weight                                                      │
#> │   --------  ------                                                      │
#> │   homicide      25                                                      │
#> │   robbery        8                                                      │
#> │   burglary       4                                                      │
#> │                                                                         │
#> │   The weighted index adds each offence's count (or rate) times its      │
#> │   severity weight; beside the unweighted total it shows whether the mix │
#> │   of offences moved, not only their number.                             │
#> ╰─────────────────────────────────────────────────────────────────────────╯