# Iterative Index Target MP

`IT5.Rd`

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

```
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.

## Value

An object of class `Rec-class`

with the `TAC`

slot populated with a numeric vector of length `reps`

## Details

The TAC is calculated as:
$$\textrm{TAC}_y = C_{y-1} I_\delta$$
where \(C_{y-1}\) is the catch from the previous year and \(I_\delta\) 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 (`Data@Iref`

) is assumed to be a proxy for MSY. In the
MSE `Iref`

is the index at MSY subject to observation error (`Obs@Irefbiascv`

).
Consequently the performance of these methods in MSE is strongly determined by the
uncertainty the in reference index.

## Functions

`IT5`

: Maximum annual changes in TAC are 5 per cent.`IT10`

: Maximum annual changes are 10 per cent.

## Required Data

See `Data-class`

for information on the `Data`

object

`IT5`

: Ind, Iref, MPrec

`IT10`

: Ind, Iref, MPrec

## Rendered Equations

See Online Documentation for correctly rendered equations

## Examples

```
IT5(1, MSEtool::SimulatedData, plot=TRUE)
#> TAC (median)
#> 1745.664
IT10(1, MSEtool::SimulatedData, plot=TRUE)
#> TAC (median)
#> 1865.308
```