Editing EconMult (section)

==Model resolution and key variables==
EconMult is a [[discrete time]] [[simulation]] model where the fleet activity is controlled by two [[Variable (mathematics)|variables]]: ''Number of vessels ('''v''')'' (within each fleet segment) and ''Number of fishing days '''d''')'' (within each time interval). ''The biomass units'' ('''''x''''') are exogenous variables. The model resolution is determined by four structural variables: ''Number of fleet groups '''j''')'', ''Number of targeted species '''n''')'', ''Number of biomass units '''i''')'' (which may be more than one within each targeted species) and ''Period length'' (time step in the simulation). The number of vessels and fishing days therefore are presented in fleet (columns)-targeted species (rows) matrices, while the biomass units is presented in a column vector ('''''X'''''):

{|
|<math>
V = \begin{pmatrix} 
v_{1,1} & \cdots & v_{1,n} \\ \vdots & \ddots & \vdots \\ v_{j,1} & \cdots & v_{j,n}
\end{pmatrix}
</math>
| style="padding-left:2em" |
<math>
D = \begin{pmatrix} 
d_{1,1} & \cdots & d_{1,n} \\ \vdots & \ddots & \vdots \\ d_{j,1} & \cdots & d_{j,n}
\end{pmatrix}
</math>
| style="padding-left:2em" |
<math>X = \begin{pmatrix} x_{1} \\ \vdots \\ x_{i} \end{pmatrix}</math>
| style="padding-left:2em" |
<math>i \ge n > 0</math><br><math>j > 0 \,\!</math>
|}