Frequently Asked Questions

1. How can I replicate some simulation results of the article of which the model is implemented in the Macroeconomic Model Data Base (MMB)?

The simple and easy way is to use the replication files. As part of the Macroeconomic Model Data Base, we provide the replication package separate from the comparison software. In that package a model code remains as close as possible to the authors' original code or article. Readme files and graphics files make reference to the specific original research findings and provide information on how we came to matching the authors' work.

2. What are the (main) differences between the original model implementation and the version integrated in the MMB platform and used for comparison?

Firstly, all model files contained in the MMB comparison software (MMB model files, hereafter) include the common model data base blocks in addition to the original model implementation in order to simulate comparable objects across models. In Modelbase blocks common MMB variables are defined, a common policy rule is written in terms of common variables, etc. In general, Modelbase blocks are separated by //******* symbols from the rest of the file. Please refer to section 3.2 of the MMB User Guide (pages 5-6) for the structure of a MMB model file.

Secondly, the model-specific monetary policy rule is commented out in MMB model files because the common policy rule is introduced.

Thirdly, we add the model economy under flexible prices and wages in a MMB model file in case the original model does not utilize a concept of output gap and therefore does not define the level of output that would be achieved under flexible prices. We add these definitions since all common monetary policy rules include reactions to output gaps.

3. What are the units of shocks commonly used in the MMB?

The MMB simulates impulse response functions to one-unit-shocks. For example, a common monetary policy shock increases on impact one percentage point in the annualized interest rate, in the absence of endogenous reaction variables in a policy rule. A common fiscal policy shock is rescaled such that it leads to one percent increase of GDP share of discretionary government expenditures. One should therefore refer to model files or model replication files to obtain the size of the shock used in the respective paper. Please refer to section 3.2.1 (page 5) of the MMB User guide where we explain how to adjust the mod-file in accordance with the different size of a shock. Section 3.3 (page 6) corresponds to the changes in the json-file.

Please note that the other comparison objects, the unconditional variance and autocorrelation functions of common variables, are computed with the empirical distributions of all shocks except for monetary policy shock.

4. How can I add a new model into the MMB?

In the new version (3.1) of the Macroeconomic Model Data Base (MMB), new models can be added using the graphical user interface. Please follow the detailed instructions of section 4 (pages 8-9) of the MMB User guide.

5. How can I use my own monetary policy rule in a comparative exercise?

There are two ways to use your own interest rate rule in the MMB as long as the rule can be expressed in terms of common MMB variables such as inflation, output or output gap. First, you can choose an option for "User-specified monetary policy rule" among a list of monetary policy rules. Then a menu with a general form for an interest rate rule will be presented. You can specify coefficient values in front of each variable. Second, you can add a new interest rate rule to a set of programmed common policy rules. Please refer to section 5 (page 10) of the MMB User guide for detailed instructions for both ways.

6. I have problems installing the MMB on my computer (first time users)

Sometimes, the mmb installation file is declared as malware by virus scanners. Depending on which software you use, you can run a quick scan of the installation file or you can deactivate the virus scanner for the time of installing the MMB. Be aware not to browse during this time, since your computer is vulnerable to malware.

In order to properly use the MMB, you also need to install Dynare and Matlab or Octave, which is a free clone of Matlab. Please refer to section 1 (page 1) of the MMB User guide for required software and setting up the MMB for the first time.

There is an "all-in-one" installation file for windows users, which installs the MMB 3.1 together with a compatible combination of Octave and Dynare. It can be downloaded in Download.

7. I have problems updating the MMB to the latest version.

In general, the MMB installer checks for currently installed MMB versions and properly uninstalls it. MMB can also be uninstalled previous to installation of the latest version. This works analogously to other software (under windows). Go to the "Control Panel", then "Programms and Features". Now, click on macromodelbase and uninstall. 

In case key folders for uninstalling the MMB have been deleted manually in the explorer, the MMB installer can not properly uninstall the current version of the MMB. It might get stuck in a loop and installation will not continue. Please cancel the installation process, go to the "Control Panel", then "Programms and Features" and uninstall the macromodelbase. Be aware that uninstalling the macromodelbase in "Apps and Features" might not be possible.