% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/adjustments.R
\name{gb_metb}
\alias{gb_metb}
\title{Apply Marginal Excess Tax Burden to public expenditure}
\usage{
gb_metb(values, rate = 0.2, vintage = NULL)
}
\arguments{
\item{values}{Numeric vector of expenditure values.}

\item{rate}{Numeric scalar. METB rate as a decimal. Default
\code{0.20}.}

\item{vintage}{Optional character. One of \code{"2003"}, \code{"2018"},
\code{"2022"}, \code{"2026"}. If supplied, overrides \code{rate} with the
bundled value for that vintage.}
}
\value{
A numeric vector the same length as \code{values}, with the
METB uplift applied.
}
\description{
Uplifts net public expenditure (or revenue raised) to reflect
the welfare cost of distortionary taxation. Default rate is
20 percent per Green Book 2022 / 2026. The historic value (2003)
was 30 percent.
}
\details{
The METB captures the welfare loss arising from raising one extra
GBP of revenue through the tax system, beyond the GBP itself.
Estimates depend on the elasticity of taxable income, the marginal
tax rate, and the distortionary margin. The Green Book reduced the
headline value from 30 percent (2003) to 20 percent (2018) in
light of post-2008 evidence.
}
\examples{
gb_metb(c(100, 200))
gb_metb(c(100, 200), vintage = "2003")
}
\references{
HM Treasury (2022). The Green Book: Central Government
Guidance on Appraisal and Evaluation, chapter on real terms and
the marginal excess tax burden.
}
\seealso{
\code{\link[=gb_appraise]{gb_appraise()}}.
}
\concept{adjustments}
