2. – The database of all supreme court decisionsfrom 1946-2016 was
compiled by Professor Spaeth ofWashingtonUniversity Lawand
covers 200+ variablesfor each decision and a database codebook
– Thisdataset was shared on Kaggle earlier thisyear (Jan 2017) and I
wanted to explore the data for more questions and some Rstudio
experience
Context
3. Description of
the dataset
– Dataset containsinformation on 8,737 SupremeCourt decisions
between 1946-2016
– Data includesthe following for each decision:
– Chief Justice who presided the court at the time of the decision
– Whether the decisionwas ‘liberal’ or ‘conservative’
– Whether the decisionwas reached after oral arguments
– Whether the decisionoverturned a prior legal precedent
– Number of Majority and Minority votes for the decision
– Number of other columns (e.g., lower court that issued prior ruling)
– Overall – the raw data was of moderate quality.For the purpose of
my analysis,I excluded a small number ofdata pointsthat were
logically inconsistent (e.g.,‘# of minority votes’> ‘# of majority
votes)
4. Questions
explored:
– Question 1:Over the last 70 yearshasthe supreme court become
more polarized /partisan?
– Challenge: hard to quantify / measure degree of polarizationor
partisanship;data unclean (e.g.,majority votes<minority votes)
– Approach: using Rstudio, check for the share of ‘liberal vs.
conservative’decisionsand ‘number of split majority vs.
supermajority vs.unanimous’decisionsunder differentChiefJustices
– Question 2:Are there fundamental differencesbetween cases where
the ruling is“split majority” vs.“unanimous” decisions?
– Approach: classified the decisionsby the type of ruling:split majority,
super majority and unanimousand plotted variableslike whether the
decision wasliberal / conservative,whether oral argumentswere used
and whether the decision overturned a prior legal precedent
5. Level of polarizationinSupreme Court decisions– by size of majorityvotes, 1946-2016
‘46 – ‘53
Polarized: inthese situations a
number of other justices
disagreed withthe decision /
reasoning
Conclusion:
Overall, the current court
(under Jus. Roberts) has fewest
share of polarizing decisions
and most unanimous decisions
Not polarized: inthese
situations all justices agreed
withthe decision / reasoning
‘53– ‘69 ‘69– ‘86 ‘86– ‘05 ‘05 – ’16*
*present Chief JusticeVariable: chief_justice
6. Level of polarizationinSupreme Court decisions– by decisionideology,1946-2016
Conclusion:
Overall, the current court
(under Jus. Roberts) has close
to an evensplit on decisions
that can be regarded as
conservative or liberal^
Influenced by high number of
liberal justices appointed by
Presidents F.D.R andTruman
(12 intotal)
*present Chief Justice
^definitions based on a detailed list of guidelines used by the raw file
Conservative^
Liberal^
‘46 – ‘53‘53– ‘69 ‘69– ‘86 ‘86– ‘05 ‘05 – ’16*
Variable: chief_justice
7. Level of polarizationbydecisionideology,1946-2016
Conclusion:
Overall, the decision ideology does
not seem tostrongly correspond to
the degree of polarization; but there
is some weak relationship
More than
2/3rd agreed
^definitions based on a detailed list of guidelines used by the raw file
Conservative^
Liberal^
Less than2/3rd
agreed
All agreed
Variable: split
8. Level of polarizationbylegal precedent treatment, 1946-2016
Conclusion:
Overall legal precedents were overturned only ina
very small number of cases. Withinthis small set,
there is more likelihoodthat the court is split (thin
majority) than unanimously agreed when
overturning the precedent
More than
2/3rd agreed
^definitions based on a detailed list of guidelines used by the raw file
No impact on legal precedents^
Legal precedent overturned^
Less than2/3rd
agreed
All agreed
Variable: split
