Many of the general equilibrium models available on this site make use of the Solver add-in to Excel to solve the underlying non-linear programming problems. This is a standard feature of Excel, but it may not be installed by default. To install the add-in if you are using Excel 2003 or earlier, open Excel and then click on the Tools menu. Select the add-ins option. The following pop-up window should appear:

If you are using Excel 2007, the dialog has been shifted. Click the Office button in the top left corner of Excel and from the drop down menu select Excel options. Select Add-in on the left hand side, then press the button marked 'Go' next to manage add-ins. This should bring up the same dialog box above. Once you have this open, select the Solver Add-in checkbox and click OK. At this point, Excel may prompt you for the original installation disks, in which case follow the onscreen guides. Once the installation is complete, you can verify that the add-in is correctly installed by going to the Tools menu in Excel 2003, where you should now see the option Solver on the menu. In Excel 2007, Solver will appear under the heading 'Analysis' on the ribbon under the Data tab.

For Mac users, VBA support, which is required for Solver, was removed from Excel 2008. However, Frontline Systems, which makes the Solver software, has recently released a free version of Solver for the Mac, which is available for download at http://www.solver.com/mac/. Please see the Frontline site for instructions on how to install and use this add-in.