# IT5: Iterative Index Target MP In DLMtool: Data-Limited Methods Toolkit

## Description

An index target MP where the TAC is modified according to current index levels (mean index over last 5 years) relative to a target level.

## Usage

 ```1 2 3``` ```IT5(x, Data, reps = 100, plot = FALSE, yrsmth = 5, mc = 0.05) IT10(x, Data, reps = 100, plot = FALSE, yrsmth = 5, mc = 0.1) ```

## Arguments

 `x` A position in the data object `Data` A data object `reps` The number of stochastic samples of the MP recommendation(s) `plot` Logical. Show the plot? `yrsmth` The number of historical years over which to average the index `mc` The maximum fractional change in the TAC among years.

## Details

The TAC is calculated as:

\textrm{TAC}_y = C_{y-1} I_δ

where C_{y-1} is the catch from the previous year and I_δ is the ratio of the mean index over the past `yrsmth` years to a reference index level. The maximum allowable change in TAC is determined by `mc`: e.g `mc=0.05` means that the maximum change in TAC from the previous catch is 5%.

The reference index level (`[email protected]`) is assumed to be a proxy for MSY. In the MSE `Iref` is the index at MSY subject to observation error (`[email protected]`). Consequently the performance of these methods in MSE is strongly determined by the uncertainty the in reference index.

## Value

An object of class `Rec` with the `TAC` slot populated with a numeric vector of length `reps`

## Functions

• `IT5`: Maximum annual changes in TAC are 5 per cent.

• `IT10`: Maximum annual changes are 10 per cent.

## Required Data

See Data for information on the `Data` object

`IT5`: Ind, Iref, MPrec

`IT10`: Ind, Iref, MPrec

## Rendered Equations

See Online Documentation for correctly rendered equations

T. Carruthers

## Examples

 ```1 2``` ```IT5(1, DLMtool::SimulatedData, plot=TRUE) IT10(1, DLMtool::SimulatedData, plot=TRUE) ```

DLMtool documentation built on March 13, 2020, 2:52 a.m.