Election indicators in Taiwan, SNTV era

I noticed that the always handy Election Indices file maintained by Michael Gallagher on his Electoral Systems page did not include Taiwan’s SNTV era of competitive elections (1992-2004). I needed the indicators for something I am working on. It just so happened that I had the candidate-level data for those years (thanks to Nathan Batto sharing them some years ago for another project). So I set out to calculate some key indices. In the off chance anyone needs them, here they are.

In the table below, “D2” is Gallagher’s “least squares” index of disproportionality (as a share, rather than percentage), “Nv” is the effective number of vote-earning parties, and “Ns” is the effective number of seat-winning parties.

year	D2	Nv	Ns
1992	0.0465	2.64	2.227
1995	0.04137	2.948	2.541
1998	0.0641	3.224	2.508
2001	0.04701	4.266	3.494
2004	0.03828	3.812	3.265

I calculated these by considering every independent candidate–and there are many of them, although not many won seats–as a separate “party.” This is the only really proper way to do these indices–especially for a purely nominal system like SNTV–if one has the data at candidate level, and in the absence of any information as to groups of these candidates being de-facto parties.

Values for Ns and Nv for these elections can be found in Bormann and Golder (as “enpp1” and “enep1”, respectively). However, my Nv values are somewhat higher because the index values in Bormann and Golder’s dataset would have been estimated from aggregated votes of “others” (including “independents”). That is, they do not take all others/independents to be one party (as is sometimes erroneously done by others), but without the candidate-level data, any such estimate could fall short of the method I am using, based on complete data on every candidate’s votes and formal party affiliation, if any. My calculations for Ns match theirs for enpp1 almost exactly, as they should, given that relatively few independents won seats (43 over the 5 elections).