Stata module to calculate various voting power indices.
vpowerin implements dynamic programming algorithms (Kurz 2016) to calculate various voting power indices. In addition, vpowerin alternatively implements generating functions and methods of direct enumeration (see options below).
You may either calculate the Shapley-Shubik power index, the absolute and the standardized Banzhaf index, or all three indices by specifying the respective options.
vpowerin also calculates the effective number of parties if required. Finally, vpowerin also estimates all possible minimal winning coalitions.
You can install the latest version of vpowerin by executing the following code:
net install vpowerin, from("https://raw.githubusercontent.com/eckerale/vpowerin/master")vpowerin requires the user-written package moremata by Ben Jann (2005) to be installed.
[by varlist:] vpowerin id weight [if] [in] [weight] [, ssi banzhaf mwc(newvar) effective gfunction enumeration generate(newvar) quota(integer) noprint]where id is a variable which uniquely identifies each player and weight is a variable which indicates each player's weight.
ssi calculates the Shapley-Shubik power index.
banzhaf calculates the absolute and the standardized Banzhaf index.
mwc(newvar) creates a series of indicator variables with stub newvar for all minimal winning coalitions indicating whether each player is part of the respective minimal winning coalition.
effective calculates the effective number of parties.
gfunction estimate voting power indices via generating functions (see, e.g., Chessa 2014 for additional information).
enumeration estimate voting power indices via method of direct enumeration.
generate(newvar) creates a new variable newvar_ssi which returns the according value of the Shapley-Shubik power index. If any of the additional options banzhaf or effective is specified, an additional variable (newvar_bi_abs, newvar_bi_std or newvar_eff, respectively) is generated which returns the corresponding value for each observation.
quota(integer) specifies the decision rule. The default option is 50 percent of the weights + 1.
noprint suppresses the output.
vpowerin requires the data to be in long format. Use the reshape command if your data are in wide format. Also note that vpowerin uses absolute weights (e.g., number of seats in the legislature).
. bysort cabinet_id: vpowerin party_id seats
. vpowerin party_id seats, ssi generate(power)
. vpowerin party_id seats, effective
. vpowerin party_id seats, banzhaf
vpowerin saves the following in r():
r(results) matrix of results
Chessa, M. 2014. A generating functions approach for computing the Public Good index efficiently. TOP 22(2): 658-73. Available from https://doi.org/10.1007/s11750-013-0286-8.
Jann, B. 2005. moremata: Stata module (Mata) to provide various functions. Available from http://ideas.repec.org/c/boc/bocode/s455001.html.
Kurz, S. 2016. Computing the power distribution in the IMF. CoRR. Available from http://arxiv.org/abs/1603.01443.
A. Ecker
Mannheim Centre for European Social Research, University of Mannheim.
Please email to alejandro.ecker@mzes.uni-mannheim.de if you observe any problems.
Thanks for citing this Stata module as follows:
Ecker, Alejandro. 2019. vpowerin: Stata module to calculate various voting power indices. Available from "https://github.com/eckerale/vpowerin".