informed” respondents are used to construct “fully informed” marginal percentages that can be
compared directly to surveyed marginal percentages. The size of information effects in collective
opinions was calculated by comparing the percentagepoint differences between surveyed and
“fully informed” collective opinions. For dichotomous questions, the statistic is
where S refers to surveyed opinion, and FI refers to the simulated “fully informed” opinion.
For surveyed opinion, R1 and R2 correspond to the percentage of responses in the first and
second response options. For “fully informed” opinion, R1 and R2 correspond to the mean of the
“fully informed” Yi probabilities (expressed as percentages) in each response category. In the
case of trichotomous variables, the comparable statistic is
This statistic, which is directly comparable between dichotomous and trichotomous
variables, takes a range of 0 to 100, with a point difference of 0 meaning that both distributions
are exactly the same and a difference of 100 meaning that they are exactly opposite. Equivalent
comparisons were used to determine the size of individuallevel information effects.
(
)
2
3
3
2
2
1
1
Difference
Point
Relative
FI

S
FI
S
FI
S
FI
S
R
R
R
R
R
R
−
+
−
+
−
=
(
)
2
2
2
1
1
Difference
Point
Relative
FI

S
FI
S
FI
S
R
R
R
R
−
+
−
=