Media, intention and final vote: A two-wave panel data study to the effects of media factors on the PvdA and VVD vote Two-wave panel data

1. Media, intention and final vote:
A two-wave panel data study to the effects of media
factors on the PvdA and VVD vote
Two-wave panel data
Assignment 8
Mark Boukes (markboukes@Hotmail.com)
5616298
1st semester 2010/2011
Dynamic Data Analysis
Lecturer: Dr. R. Vliegenthart
January 28, 2010
Communication Science (Research MSc)
Faculty of Social and Behavioural Sciences
University of Amsterdam

3. Table of contents
INTRODUCTION AND THEORY........................................................................................................................1
METHOD........................................................................................................................................................2
RESULTS........................................................................................................................................................4
MAXIMUM LIKELIHOOD ESTIMATION WITH BINARY LOGISTIC REGRESSION..........................................................................................4
CONCLUSION.................................................................................................................................................6
REFERENCE....................................................................................................................................................7
APPENDIX A: TELEVISION PROGRAMS USED TO CONSTRUCT THE INDEPENDENT VARIABLES..........................7
APPENDIX B: DO FILE.....................................................................................................................................8

5. Media, intention and final vote:
A two-wave panel data study to the effects of media
factors on the PvdA and VVD vote
Mark Boukes
Introduction and theory
In this study, I aim to investigate 1) certain assumptions that are often made by politicians but
also communication scholars and 2) a more investigated and well-known theory. First, I will
test whether certain media really have the political influence that is assumed by some people.
It is frequently said that programs of public broadcasters belong to the ‘left church’ and that
De Volkskrant is a left newspaper, whereas De Telegraaf is a newspaper with right-wing
sympathies; Algemeen Dagblad, NRC Handelsblad and the commercial broadcasters seem to
have a less obvious political stance. This study investigates whether these media indeed have
the effect on their viewers and readers as often is assumed. In the period before elections an
increase in media attention for this democratic process is logically expected; therefore, it is
also reasonable to expect potential effects to take place in that period. Furthermore, the well-
known bandwagon-effect (McAllister & Studlar, 1991) will be tested; are voters who expect
that a party will win many seats in Parliament more likely to vote for that party, than voters
who expect a less good result?
I will focus on (potential) voters of two parties: the PvdA (socialists) and VVD
(liberals). The decision to choose these two parties is based on poll and election results (see
also Figure 1) and the characteristics of the parties. First, the PvdA is a left-wing party,
whereas the VVD is a right-wing party, which makes it interesting to compare the effects on
both parties. Furthermore, the PvdA lost many seats in the last weeks before the elections
according to the poll results the Politieke Barometer of Interview-NSS (now Synovate), what
makes it interesting to find potential causes of the losses.
Consequently, four hypotheses will be tested focusing on the effects of television,
newspapers and expectations.
• H1: Viewers of public broadcasting programs will be more likely to change their
political preference in a left political direction in the period before the elections and
therefore are more likely to vote for the PvdA at the time of the elections, whereas
they are less likely to vote for the VVD, compared to a first measure of vote intention
some weeks before the elections.
1

6. • H2: Readers of De Telegraaf will be more likely to vote for the VVD at the time of the
elections, whereas they are less likely to vote for the PvdA, compared to a first
measure of vote intention some weeks before the elections.
• H3: Readers of De Volkskrant will be more likely to vote for the PvdA at the time of
the elections, whereas they are less likely to vote for the VVD, compared to a first
measure of vote intention some weeks before the elections.
• H4: People, who estimate the number of seats a political party will win in the elections
higher, will be more likely to vote for that party, than those who estimate this number
lower, compared to a first measure of vote intention some weeks before the elections.
Figure 1. Poll results of the weeks before the 2006 Dutch Parliamentary election and the election results
Method
To investigate the hypothesis a two-wave panel survey was used, the ‘Dutch Parliamentary
Election Studies 2006’1. Statistics Netherlands (CBS) carried out the fieldwork; interviews
were conducted face-to-face or by telephone; via a self-completion questionnaire the second
part of the questions were posed. A two-stage procedure was followed to find the sample of
respondents: first, municipalities were selected with unequal chances to the number of persons
in the municipalities; second, persons living in the selected municipalities had an equal
chance to be invited to participate in the survey. The total non-response rate of the survey was
51.7 percent. The survey was rather representative for the Dutch population, though people
1
http://www.dpes.nl/pages/nko_2006.php
2

7. with a non-Western origin were underrepresented. The dataset contained the answers of
almost 2000 respondents (N = 1,895).
The dependent variable in this study is measured in the second wave by the question
‘Which party did you vote for at the elections of 22 November?’ and the lagged dependent
variable was measured in the first wave by the question ‘Which party will you vote for at the
elections of 22 November?’ (with a do-not-know-yet possibility). Dummy variables were
created for either having voted on the PvdA, having voted on the VVD (both wave 2), having
had the intention to vote for the PvdA, and having had the intention to vote for the VVD (both
wave 1).
In an original way, via an additive score for the variables indicating how often
particular programs are watched (1-5 scale, never – almost daily), the two independent
variables were created to measure how often respondents watch public broadcasting television
or commercial television. For both variables, the same number of programs were chosen
which are highly similar; for example, when a talk show was chosen for commercial
broadcasters also a similar talk show was chosen for the public broadcaster; the news on the
Dutch public broadcaster NOS was included, so the news on commercial broadcaster RTL4
was also included, etc. In total, for both independent variables (‘watching public
broadcasting’ and ‘watching commercial broadcasting’) eight similar programs were selected
(see Appendix A for the programs).
Furthermore, variables were already present in the dataset for if the people read certain
newspapers; those just needed to be recoded into dummy variables. To investigate the presence
of a bandwagon-effect, the variables were used that were obtained by the question ‘How many
seats do you think [party] will get in the next elections?’. Because some respondents answered
with numbers that were obviously not credible (lower than 10 or more than 40 for the VVD /
lower than 10 or more than 60 for the PvdA), those were set to missing, just as was the case for
the respondents who did not answer this question.
Next to this, control variables were created or changed for the analysis. Age was
calculated by subtracting the year of birth from 2006. Gender was measured by a dummy for
being male. Dummy variables were also created for education; respondents either completed
low level education, middle level education or high level education. The household income
was already measured in a useable way. A dummy was created for being religious.
To analyse the effects of the different media on the real vote of respondents a logistic
regression analyses was conducted using Stata 10.1. The analysis controlled for the lagged
dependent variable, which is the intention to vote or not for a certain party some weeks before
3

8. (in wave 1). A logistic regression was necessary to investigate the effect on the odds of
respondents having voted for one party (score 1) or not (score 0). An inspection of the outliers
of this model showed that some respondents stand out with high standardized residuals,
however these cases seem to represent natural deviations, not miscoded observations or wrong
interpretations and are therefore kept in the sample; except, as specified above, for those with
strange estimates for the number of seats a party would gain.
Results
Before the results of the logistic analysis are presented, first an overview will be presented so
it is clear how much the real votes vary from the intentions people had to vote. Table 1 shows
the number of voters who did and who did not change their vote compared to their intention
to vote for one of the parties. It becomes clear that of only about 10 percent of the voters the
real vote differs from the intended vote. Via the logistic regression analysis it was investigated
which media factors could have caused these differences.
Table 1. Variation between vote intention and real vote
Intention to vote PvdA Intention to vote VVD
No Yes No Yes
Voted PvdA
Voted VVD
No 1,478 47 No 1,611 32
Yes 154 216 Yes 113 139
Maximum likelihood estimation with binary logistic regression
The binary logit model with vote in the election for a party as dependent variable; frequency
of watching public broadcasting, frequency of watching commercial broadcasting, reading
certain newspapers and the estimation of the number of seats that party will get in the election
as independent variables; age, sex, education, income and religiosity as control variables; and
finally the intention to vote for that party a few weeks before as lagged dependent variable,
reduces the error in the prediction of the binary variable with 56.6 % for the model with
voting for the PvdfA as dependent variable and with 50.0 % for the model with voting for the
VVD as dependent variable according to the adjusted count R2. The results of these models
can be found in Table 3.
4

9. Table 2. The effects of the independent variables on the odds of having voted for a party (PvdA/VVD)
PvdA vote VVD vote
Odds ratios (SE) Odds ratios (SE)
Intention to vote for this party (1 =Yes, 0 = No) 75.336 (23.187)** 65.049 (21.027)**
Watching public broadcasting 1.404 (0.249) # 0.915 (0.172)
Watching commercial broadcasting 1.046 (0.189) 0.923 (0.182)
Reading De Telegraaf (1 = Yes, 0 = No) ##
0.539 (0.171) 2.673 (0.729)**
Reading De Volkskrant (1 = Yes, 0 = No) 1.054 (0.353) 0.488 (0.208)
Reading Algemeen Dagblad (1 = Yes, 0 = No) 0.923 (0.291) 1.716 (0.521)
Reading NRC Handelsblad (1 = Yes, 0 = No) 0.773 (0.304) 1.450 (0.534)
Estimated number of seat for party 1.044 (0.019)* 0.998 (0.020)
Age 0.985 (0.008) 0.982 (0.009)**
Male (1 = Yes, 0 = No) 0.664 (0.157) 0.915 (0.236)
Low level education (ref. Middle) 0.904 (0.327) 0.641 (0.266)
High level education (ref. Middle) 0.876 (0.240) 0.870 (0.252)
Income 1.012 (0.023) 1.037 (0.024)
Religious (1 = Yes, 0 = No) 0.590 (0.142)* 0.572 (0.146)*
Observations (N) 973 904
Adjusted count R2 / Nagelkerke R2 0.566 / 0.564 0.500 / 0.525
χ2 430.00 340.98
BIC -6043.753 -5566.993
Cells contain odd ratios, exp(b); with standard errors in parentheses
#
p = 0.056, # p = 0.052,* p < 0.05, ** p < 0.01
The exponentials of the coefficients estimated by the binary logit models, odds ratios, indicate
that whether variables positively (coefficients above 1) or negatively (coefficients below 1)
affect the likelihood that a respondents votes for a party. Logically, the effects of the lagged
dependent variable ‘Intention to vote for this party’ are large and positive, more interesting
are the other effects.
Starting with the first hypothesis, watching more frequently public broadcasting makes
it more likely that respondent have voted for the PvdA, whereas this has no influence on the
likelihood of voting for the VVD. A one-point increase in watching public broadcasting raises
the odds of voting for the PvdA by a factor of 1.404, holding the other variables constant.
Following a two-tailed test with 95% confidence interval, this effect is not significant;
however, because this effect was hypothesized to be positive, a one-tailed test is allowed and
it is thus possible to conclude that watching programs of public broadcasters makes
respondents more likely to vote for the PvdA (χ2 = 3.66, p = 0.06) compared to their intention
a few weeks before the elections. As expected, watching commercial broadcasting has no
significant effects on the likelihood of voting for one of the two parties.
5

10. De Telegraaf is the only print medium that has a significant effect on the votes. When
we inspect the coefficients belonging to reading the newspapers included in the analysis, it
becomes clear that reading all the other newspapers does not significantly increase or decrease
the likelihood of voting for the PvdA or the VVD. However, reading De Telegraaf does this
and also in the direction that was expected, therefore again one-tailed tests were allowed.
Reading De Telegraaf significantly raises the odds of voting for the VVD by a factor of 2.673
(χ2 = 13.00, p < 0.01), whereas it significantly decreases the odds of voting for the PvdA by a
factor of 0.539 (χ2 = 3.78, p = 0.052). The hypothesised effects of reading De Volkskrant were
rejected as it seems not to influence the odds of voting for the PvdA significantly (χ2 = 0.02, p
= 0.88) and the effect on the odds of voting for the VVD was only marginally significant (χ2 =
2.83, p = 0.09). However, this last effect was indeed in the expected direction, as reading De
Volkskrant decreases the odds of voting VVD by a factor of 0.488.
Finally, the so-called bandwagon effect seems only to be found partially by this
analysis. It seems only for the PvdA vote the case that as higher respondents expect the
number of seats that party will get after the election, the more likely it will become they vote
for the PvdA. For every one seat higher estimation of the election results, the odds of voting
for the PvdA significantly increases by a factor of 1.044 (χ2 = 5.83, p < 0.05). A similar effect
was not found for the VVD voters (χ2 = 0.01, p = 0.94).
Conclusion
This study has found some interesting results. First of all, the stimulating influence of
watching public broadcasters’ programs on the intention to vote for the PvdA. The likelihood
of this increases by seeing those programs and as this study controls for many possible
confounding variables, this might indicate certain content in those programs that are
favourable for the PvdA and perhaps other left-wing parties too. This is remarkable since of
the programs that were taken into consideration, only two of the eight were produced by the
VARA, a public broadcaster that is related to the PvdA in various ways. Therefore, other
characteristics of those programs might explain why watching these programs increases the
odds of voting for the PvdA, but does not influence the odds of voting for the VVD. A similar
but contradictory conclusion is that reading De Telegraaf increases the odds of voting for the
VVD, while it decreases the odds of voting for the PvdA. Probably a characteristic of this
newspaper underlies this effect. To understand both effects better, content analysis might be
helpful. Nevertheless, the results seem to confirm the left-wing identity of the public
broadcasting system and the right-wing identity of De Telegraaf. It was not possible to
6

11. conclude straightforwardly whether a bandwagon effect took place in this study. While it
seems a cause for voting the PvdA, the estimation of the number of seats the VVD gets in the
election did not influence the final vote for that party.
Though results could possibly be biased by sensitization to the questions (Romer,
Kenski, Winneg, Adasiewicz & Jamieson, 2006), the two-wave panel design had the large
benefit that it was possible to include a lagged dependent variable, and thereby control for the
past political preferences of respondents. Therefore, we can be surer that the respondents were
influenced by the media in the weeks between the two measures, in which it is also likely,
because there probably was a lot of media attention for politics as the elections were coming
near. This influence seemed to be in the direction that was expected for the public
broadcasting programs and De Telegraaf and the assumptions that are often expressed about
these can therefore be substantiated with the results of this study.
Reference
McAllister, I., & Studlar, D. T. (1991). Bandwagon, underdog, or projection?: Opinion polls
and electoral choice in Britain, 1979-1987. The Journal of Politics, 53, 720-740.
Romer, D., Kenski, K., Winneg, K., Adasiewicz, C., & Jamieson, K. H. (2006). Capturing
campaign dynamics 2000 & 2004: The National Annenberg Election Survey.
Philidelphia: University of Pennsylvania Press.
Appendix A: Television programs used to construct the independent variables
Public broadcasting Commercial broadcasting
Onderweg naar morgen (Ned. 3) Goede Tijden, Slechte Tijden (RTL4)
EenVandaag (Ned. 1) Editie NL (RTL4)
De Wereld Draait Door (Ned. 3) Boulevard (RTL4)
Man Bijt Hond (Ned. 2) Big Brother (Talpa)
NOS 8 uur journal (Ned. 1) RTL4 Nieuws (RTL4)
NOVA, Den Haag Vandaag (Ned. 2) Hart van Nederland (SBS6)
Netwerk (Ned. 2) Shownieuws (SBS6)
Pauw en Witteman (Ned. 1) Jensen! (RTL5)
7

12. Appendix B: Do File
*Assignment8
clear
set memory 250m, permanently
set more off, permanently
use H:DDANKO2006
tab v081
tab v081, nol
gen pvda2006intention = 0
replace pvda2006intention = 1 if v081==2
gen vvd2006intention = 0
replace vvd2006intention = 1 if v081==3
tab v512
tab v512, nol
gen pvda2006vote = 0
replace pvda2006vote = 1 if v512==2
gen vvd2006vote = 0
replace vvd2006vote = 1 if v512==3
//all measures have a 911 out of 2806 people get the answer PA(means not
measured in this wave), those will therefore be dropped
drop if v936==994
****Media independent variables
*programs on commercial television
tab v868
tab v853
tab v854
tab v859
tab v861
tab v863
tab v864
tab v870
tab v868, nol
tab v853, nol
tab v854, nol
tab v859, nol
tab v861, nol
tab v863, nol
tab v864, nol
tab v870, nol
replace v868=.a if v868==997
replace v853=.a if v853==997
replace v854=.a if v854==997
replace v859=.a if v859==997
replace v861=.a if v861==997
replace v863=.a if v863==997
replace v864=.a if v864==997
replace v870=.a if v870==997
pwcorr v868 v853 v854 v859 v861 v863 v864 v870
egen commtv = rowmean(v868 v853 v854 v859 v861 v863 v864 v870)
egen commtv_m = rowmiss(v868 v853 v854 v859 v861 v863 v864 v870)
replace commtv = .a if commtv_m>3
sum commtv
tab commtv , miss
histogram commtv
8

13. graph box commtv
*programs on public broadcasting tv
tab v857
tab v852
tab v860
tab v855
tab v867
tab v871
tab v856
tab v872
tab v857, nol
tab v852, nol
tab v860, nol
tab v855, nol
tab v867, nol
tab v871, nol
tab v856, nol
tab v872, nol
replace v857=.a if v857==997
replace v852=.a if v852==997
replace v860=.a if v860==997
replace v855=.a if v855==997
replace v867=.a if v867==997
replace v871=.a if v871==997
replace v856=.a if v856==997
replace v872=.a if v872==997
corr v857 v852 v860 v855 v867 v871 v856 v872
pwcorr v857 v852 v860 v855 v867 v871 v856 v872
alpha v857 v852 v860 v855 v867 v871 v856 v872
egen pbstv = rowmean(v857 v852 v860 v855 v867 v871 v856 v872)
egen pbstv_m = rowmiss(v857 v852 v860 v855 v867 v871 v856 v872)
replace pbstv = .a if pbstv_m>3
sum pbstv
tab pbstv , miss
histogram pbstv
graph box pbstv
***Other media variables***
tab v016
tab v016, nol
recode v016 (1=1 Yes) (2=0 No) (997=.a) (998=.a) (999=.a), gen(Telegraaf)
tab Telegraaf
tab v017
tab v017, nol
recode v017(1=1 Yes) (2=0 No) (997=.a) (998=.a) (999=.a), gen(Volkskrant)
tab Volkskrant
tab v019
tab v019, nol
recode v019(1=1 Yes) (2=0 No) (997=.a) (998=.a) (999=.a), gen(NRC)
tab NRC
tab v020
tab v020, nol
recode v020(1=1 Yes) (2=0 No) (997=.a) (998=.a) (999=.a), gen(AD)
tab AD
9

14. **************Prepare the other independent variables *******
tab v104
tab v104 , nol
replace v104=.a if v104==997|v104==998
tab v104, missing
gen estimatePvdASeats=v104
tab v103
tab v103 , nol
replace v103=.a if v103==997|v103==998
tab v103, missing
gen estimateVVDSeats=v103
tab v421, miss
gen age = 2006-v421
sum age
tab age, miss
tab v420, miss
tab v420, nolabel
recode v420(2=0 Female) (1=1 Male), gen(male)
tab male,miss
*highest education completed
tab v430
tab v430, nol
recode v430(1=0 elementary) (2=1 vocational) (3=2 secondary) (4=3
higherLevel) (5=4 university) (997=.a), gen(education)
tab v430
tab education, miss
tab education, nol
gen loweducation=0
replace loweducation=1 if education==0|education==1
replace loweducation=.a if education==.a
gen middleeducation=0
replace middleeducation=1 if education==2|education==3
replace middleeducation=.a if education==.a
gen higheducation=0
replace higheducation=1 if education==4
replace higheducation=.a if education==.a
tab loweducation,miss
tab middleeducation,miss
tab higheducation,miss
*household income corrected for hh size
tab v414, miss
tab v414, nol
gen income=v414
replace income=.a if income==998
tab income
tab v425
tab v425, nol
recode v425(2=0 notReligious) (1=1 Religious), gen(religious)
tab religious, miss
replace religious=.a if religious==997
10

15. tab religious, miss
tab religious, nol
logit pvda2006vote pvda2006intention commtv pbstv NewspaperT1 NewspaperT2
Telegraaf Volkskrant NRC AD Metro Spits EncounterPollsT1 EncounterPollsT2
seenDebatesEntirely seenNoDebates MatchmakerPVDA MatchmakerSP
estimatePvdASeats Turkey_EU age male loweducation higheducation income
religious
*Just AR(1)
logit pvda2006vote pvda2006intention
listcoef
*AR(1) plus controls
logit pvda2006vote pvda2006intention age male loweducation higheducation
income religious
listcoef
*AR(1) plus controls plus tv
logit pvda2006vote pvda2006intention commtv pbstv age male loweducation
higheducation income religious
listcoef
*AR(1) plus controls plus tv plus newspaper
logit pvda2006vote pvda2006intention commtv pbstv Telegraaf Volkskrant AD
NRC age male loweducation higheducation income religious
listcoef
**diagnostics
predict rstd, rs
label var rstd "Standardized Residual"
sort rstd , stable
list rstd rnr pvda2006vote pvda2006intention commtv pbstv Telegraaf age male
loweducation higheducation income religious if (rstd>2.5|rstd<-2.5)&rstd!=.
predict cook, dbeta
graph twoway scatter cook rnr, ylabel(0(.01).05) xtitle("RNR") yline(.1 .2)
msymbol(none) mlabel(rnr) mlabposition(0)
list pvda2006vote pvda2006intention commtv pbstv Telegraaf Volkskrant AD NRC
age male loweducation higheducation income religious estimatePvdASeats
Turkey_EU if rnr==4078|rnr==1729|rnr==3366
//remove uncredible estimates of pvda seats
tab estimatePvdASeats
replace estimatePvdASeats =.a if estimatePvdASeats<10
replace estimatePvdASeats =.a if estimatePvdASeats>60
tab estimatePvdASeats
tab estimateVVDSeats
sum estimateVVDSeats
replace estimateVVDSeats=.a if estimateVVDSeats<10
replace estimateVVDSeats=.a if estimateVVDSeats>40
tab estimateVVDSeats
logit pvda2006vote pvda2006intention commtv pbstv Telegraaf Volkskrant AD
NRC estimatePvdASeats age male loweducation higheducation income religious
drop rstd cook
predict rstd, rs
label var rstd "Standardized Residual"
sort rstd , stable
11

16. list rstd rnr pvda2006vote pvda2006intention commtv pbstv Telegraaf age male
loweducation higheducation income religious if (rstd>2.5|rstd<-2.5)&rstd!=.
predict cook, dbeta
graph twoway scatter cook rnr, ylabel(0(.01).05) xtitle("RNR") yline(.1 .2)
msymbol(none) mlabel(rnr) mlabposition(0)
list cook rstd pvda2006vote pvda2006intention commtv pbstv Telegraaf
Volkskrant AD NRC age male loweducation higheducation income religious
estimatePvdASeats Turkey_EU if rnr==1797|rnr==1717|rnr==1729|rnr==1228|
rnr==1927|rnr==2751
*test for heteroscedasticity
hetprob pvda2006vote pvda2006intention commtv pbstv Telegraaf Volkskrant AD
NRC age male loweducation higheducation income religious estimatePvdASeats,
het(pvda2006intention commtv pbstv Telegraaf Volkskrant AD NRC age male
loweducation higheducation income religious estimatePvdASeats)
* not significant, no heteroscedasticity, so robust estimation is not
necessary
*test for multicollinarity
collin vvd2006vote vvd2006intention pbstv commtv Telegraaf Volkskrant AD NRC
estimateVVDSeats age male loweducation higheducation income religious
**check for wrong codings
tab pvda2006vote, nol
tab pvda2006intention , nol
tab commtv , nol
tab pbstv , nol
tab Telegraaf , nol
tab Volkskrant , nol
tab AD , nol
tab NRC , nol
tab age , nol
tab male , nol
tab loweducation , nol
tab higheducation , nol
tab income , nol
tab religious , nol
tab estimatePvdASeats , nol
tab Turkey_EU, nol
tab vvd2006vote , nol
tab vvd2006intention , nol
tab estimateVVDSeats
*inspection of change
tab pvda2006vote pvda2006intention
tab vvd2006vote vvd2006intention
**Final models
logistic pvda2006vote pvda2006intention pbstv commtv Telegraaf Volkskrant AD
NRC estimatePvdASeats age male loweducation higheducation income religious
fitstat
test pbstv
test Telegraaf
test Volkskrant
test estimatePvdASeats
logistic vvd2006vote vvd2006intention pbstv commtv Telegraaf Volkskrant AD
NRC estimateVVDSeats age male loweducation higheducation income religious
fitstat
test pbstv
test Telegraaf
12

17. test Volkskrant
test estimateVVDSeats
13