Asymmetric media responses in the Dutch context

Does newspapers coverage respond to economic information?

Autoregressive Distributed Lags and Error

Correction Models

Assignment 5

Mark Boukes (markboukes@Hotmail.com)5616298

1st semester 2010/2011Dynamic Data Analysis

Lecturer: Dr. R. VliegenthartDecember 16, 2010

Communication Science (Research MSc) Faculty of Social and Behavioural Sciences

University of Amsterdam

Table of contents

INTRODUCTION...................................................................................................................................................1

METHOD.................................................................................................................................................................1

RESULTS.................................................................................................................................................................2

AUTOREGRESSIVE DISTRIBUTED LAGS MODEL.......................................................................................................3

ERROR CORRECTION MODEL.................................................................................................................................7

CONCLUSION........................................................................................................................................................9

REFERENCE........................................................................................................................................................10

Do File

IntroductionIn this study, I aim to investigate the influence the economy has on newspaper coverage. With

this, I try to repeat the analysis of Soroka (2006) in a Dutch context. Soroka found that

newspaper coverage about unemployment in the United Kingdom was stimulated by real

developments in the economy, the unemployment rate. However, he also found that negative

changes in the unemployment rate had a much bigger effect on newspaper coverage than

positive developments. My expectation is that this could also be the case in the Netherlands as

Hollanders and Vliegenthart (2009) showed that news coverage was negatively affected by the

stock market’s performance.

To study the effect of unemployment on newspaper coverage, aggregate-level time-

series data for the Netherlands were used from January 1990 to December 2000. I had two

hypotheses:

o H1: Changes in the unemployment rate have an effect on the number of articles published

about unemployment.

o H2: Positive changes in the unemployment rate (economy gets worse) have a stronger

effect on the number of articles published about unemployment than negative changes.

MethodIn order to investigate whether changes in unemployment rate have an effect on Dutch

newspaper coverage, a dataset was created via a computer-assisted content analysis, which

was conducted using the digital archive of the Web-based version of LexisNexis. Articles

were selected via the Boolean search term ‘werkloosheid OR werkeloosheid’. The period that

I analyzed was 1 January 1990 until 31 December 2000, as the analyses of Soroka (2006) also

stopped in the year 2000 and LexisNexis contains no Dutch data for the period before 1990.

Only articles in NRC Handelsblad were analyzed, as this is the only newspaper that contains

data from 1990 on in LexisNexis. Using other newspapers would have led to a too short

period. The search resulted in 7652 articles for the whole period. The number of articles was

aggregated, resulting in weekly visibility scores of unemployment in NRC Handelsblad.

The variable representing the unemployment rate was obtained via the website of

Eurostat; also for the period 1990-2000. Unemployment rate was measured as the percentage

of the total labour force. However, as this data was monthly and not weekly, the

unemployment rate for intervening moments were calculated by taking the mean of the week

before and the next week measured. Because I want to reproduce the study of Soroka in the

Dutch context, it was necessary to transform the unemployment rate variable in a variable that

indicates the difference in unemployment rate between two time points. In addition, this

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differenced unemployment rate variable was used to create to variables ΔUnemployment rate

(negative) and ΔUnemployment rate (positive). In the first, the values are the same as the

differenced variable if changes are negative (unemployment decreases), if changes are

positive the value of this variable is zero. ΔUnemployment rate (positive) copies the values of

the differenced unemployment rate in cases when changes are positive (unemployment

increases), whereas values are zero if changes are negative (unemployment decreases).

Autoregressive Distributed Lags and Error Correction Models were conducted in Stata

10.1, to analyse the effects of the unemployment rate on newspaper coverage. Doing this, I

followed the stepwise approach described by De Boef and Keele (2008). First the general

model was built, which has the lagged dependent variable in it and the contemporary and

lagged value of the independent variable. Second, valid restrictions were imposed on this

model . Finally, the results were interpreted.

ResultsIn this results section, the outcomes of both an Autoregressive Distributed Lags model and an

Error Correction Model are described as both models have unique advantages; ADL models

estimated short-term effects directly, whereas ECMs are better in avoiding spurious findings

(De Boef & Keele, 2008).

Figure 1 plots the time series of the number of articles in NRC Handelsblad about

unemployment and the unemployment rate itself. The number of articles about unemployment

seems to be quite stable over time, and that is also what augmented Dickey-Fuller tests

confirm (see Table 1). Because I did not use the unemployment rate itself, but the differenced

series, it was likely that a unit root was also not present in this series; augmented Dickey-

Fuller tests confirmed this. Hypotheses for unit root are rejected for all time-series conducted

in this study, so the data are treated as stationary and I did not need to integrate the data.

Table 1. The results of augmented Dickey-Fuller tests the number of articles and unemployment rate

Augmented Dickey-Fuller testArticles in

NRCΔ in

Unemployment rateΔUnemployment

rate (negative)ΔUnemployment

rate (positive)Random walk without drift -5.045 -21.719 -16.057 -13.831

Random walk with drift -14.515 -21.760 -21.073 -17.029

Random walk with drift and trend -14.718 -21.817 -21.057 -17.206

Note. All tests indicate the absence of a unit root.

Next the Autoregressive Distributed Lags Model and the Error Correction Model are described

both for the independent variable ‘difference in unemployment rate’ and for the asymetric

model with the same independent variable, that was split in two (positive and negative).

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Figure 1. Number of articles about unemployment and unemployment rate between 1990 and 2000.

Autoregressive Distributed Lags Model

I started my analysis with a general model as De Boef and Keele (2008) recommended,

because substantive theory does not provide enough guidance for precise dynamic

specifications; I was only sure about the exogeneity of the unemployment rate. The general

models were defined as follows:

Articles t = α0 + ( αi*Articles t-i ) + β0*ΔUnemployment t + β1*ΔUnemployment t-1 + ε t

Articles t = α0 + ( αi*Articles t-i )+ β0*ΔUnemployment(positive) t +

β1*ΔUnemployment(positive) t-1+ β2*ΔUnemployment(negative) t +

β3*ΔUnemployment(negative) t-1 + ε t

where Articles is the number of articles published in NRC Handelsblad about unemployment

and |αi| should be less than 1 so the time-series is stationary, ΔUnemployment is the indicator

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of the differences in the unemployment rate, α0 is the constant of the model and ε is the error

term. The first model test for the simple symmetric effect of changes in unemployment on the

number of articles, whereas the second model makes a difference between positive and negative

changes in the unemployment rate, to test whether those have different effects. The general

model takes lag one to four into account, because the general model with the dependent

variable having only one lag showed considerable autocorrelation; for the symmetric model

for example, Ljung–Box Q test statistic for autocorrelation (Q = 111.69, p < .001) and the

Engle-Granger test for the presence of conditional heteroscedasticity (Q = 32.22, p = .041)

were both significant. Table 2 shows the coefficients of both the symmetric and the asymmetric

model.

Table 2. Autoregressive Distributed Lags Models: unemployment rate and news coverage

 General model

(symmetric)General model (asymmetric)

Dead Start model (symmetric)

Dead Start model (symmetric)

Articles t-1 .330** .333** .327** .329**(.041) (.042) (.041) (.041)

Articles t-2 .134** .132** .135** .132**(.044) (.044) (.043) (.043)

Articles t-3 .083* .080* .083* .084*(.044) (.044) (.043) (.043)

Articles t-4 .124** .129** .125** .135**(.042) (.043) (.041) (.042)

ΔUnemployment t -1.949(2.166)

ΔUnemployment t-1 -2.596 -2.788(2.164) (2.153)

ΔUnemployment(positive) t 1.754(4.686)

ΔUnemployment(positive) t-1 -8.462 * -7.063*

(4.655) (4.027)

ΔUnemployment(negative) t -4.585(4.160)

ΔUnemployment(negative) t-1 2.297 1.147

(4.100) (3.801)

Constant 4.339** 4.461** 4.340** 4.510**

(.670) (.685) (.669) (.683)

Ljung-Box Q(20) residuals 22.86 24.82 21.95 24.44

Ljung-Box Q(20) residuals² 16.63 17.03 17.04 18.04

R2 / Adjusted R2 0.273 / 0.266 0.276 / 0.266 0.272 / 0.266 0.274 / 0.266Note. Cells contain OLS unstandardized regression coefficients with standard errors in parentheses;

* p < .10, ** p < .01

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The symmetric and the asymmetric model fit the data equally well; both explain 26.6 percent

of the variance in the number of articles. However, almost none of the independent variables

have a significant effect. The general effect of changes in the unemployment rate (in the

symmetric model) has no significant impact on the number of articles published in NRC

Handelsblad about unemployment. As expected the only effect that is significant is the one of

increases in unemployment (bad economic news) at lag 1 in the asymmetric model. However,

this effect is in the opposite direction as I expected; a 1-point increase in unemployment will

result in about 8 fewer articles in the next week. The effect of negative changes in the

unemployment rate (when unemployment decreases) is not significant.

Because none of the contemporary effects of changes in unemployment are significant

and it seems more likely that newspaper coverage is affected by previous unemployment rates

than contemporary ones, because journalists plan their articles some days or a week before

(e.g., arranging interviews), I restricted those to be zero; resulting in a Dead Start model (see

De Boef & Keele, 2008, p.187). To be sure the estimates of the Dead Start models are not

worse than those of the general models, the differences in R2 between the general models and

the Dead Start models are taken into account. Those differences are very minor (see Table 2);

therefore, the restrictions can be assumed to be appropriate. Results of the Dead Start models

can be found in Table 2.

These results lead to the same conclusions as the ones from the general model: the

effect of changes in unemployment rate are not significant in the symmetric model, and in the

asymmetric model are only the positive changes significant. A 1 percent increase of the

unemployment in the Netherlands, would lead to a decrease of 7 articles about this topic in the

next week.

The Dead Start model thus looks like this for the symmetric model:

Articles t = 4.340 + .327*Articles t-1 + .135*Articles t-2 + .083*Articles t-1 + .125*Articles t-4 +

-2.788*ΔUnemployment t-1 + ε t

The asymmetric Dead Start model looks like this:

Articles t = 4.510 + .329*Articles t-1 + .132*Articles t-2 + .084*Articles t-1 + .135*Articles t-4 +

-7.063*ΔUnemployment(positive) t-1+ 1.147*ΔUnemployment(negative) t-1 + ε t

As I have interpreted the short run effect of changes in unemployment before, now I will

focus on the effects in the long run. Therefore, I use the long run multiplier (LRM), which

indicates the total effect of an independent variable, because it takes into account that an

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effect is distributed over several future time periods. De Boef and Keele (2008) gave the

following formula to calculate the long run multiplier: k1 = (β1 + β0) / (1-α1). However, this

formula does not take into account that the dependent variable has multiple lags in the model,

like here is the cases with Articles t-1 to Articles t-4 in the model. Therefore, it was necessary to

calculate the LRM by hand. The LRM of differences in unemployment in the symmetric Dead

Start model was -5.23. This means that a one percent increase in unemployment, leads in the

long run to about five articles less being published about unemployment. The median lag

length of this effect is 1; this means that half of the total effect is already reached within the

first lag. The mean lag length, how long it takes to move back to the equilibrium is 6, after

this lag the LRM increases with less than 0.01 points. How the LRM is distributed over time

and what the effects are per lag is shown in Figure 2.

Figure 2. Left: Long Run Multiplier Graph of the effect of an increase in unemployment on newspaper coverage. Right: Effect of unemployment per lag.

Calculating the LRM by hand also made me understand this process better and therefore I was

able to come up with a formula for the long run multiplier in Dead Start ADL models with

multiple lags:

k1 = ( (β1) / (1 – α i) ) - β1*(j - 1)

where i > 0 (to not take the constant into account) and j is the number of independent variables.

Applying this formula (or calculating by hand) to the asymmetric model, finds that an

increase in unemployment with one percent, leads in the long run to a total of -13.35 fewer

articles that are published (Figure 3 displays the Long Run Multiplier of the different lags).

The median lag length of this effect is 1; this means that already more than half of the effect

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takes place during the first lag (between t0 and t1). The mean lag length, how long it takes to

move back to the equilibrium is 6, after this lag the LRM increases with less than 0.03 points.

Figure 3. Left: Long Run Multiplier Graph of the effect of an increase in unemployment on newspaper coverage. Right: Effect of unemployment per lag.

On the other hand, a decrease of one percent in unemployment (negative change) results in

the long run to a total of only 2.17 articles fewer articles being published. The median lag

length of this effect is also 1. The mean lag length, how long it takes to move back to the

equilibrium is 5, after this lag the LRM increases with less than 0.03 points.

Error Correction Model

The analyses above are repeated here with the same data, but now with Error Correction

Models instead of Autoregressive Distributed Lags Models. General models were again

starting points of the procedure, they were defined respectively for the symmetric and the

asymmetric models as follows:

ΔArticles t = α0 + ( αi*Articles t-i) + β0*ΔΔUnemployment t + β1*ΔUnemployment t-1 + ε t

ΔArticles t = α0 + ( αi*Articles t-i ) + β0*ΔΔUnemployment(positive) t +

β1*ΔUnemployment(positive) t-1+ β2*ΔΔUnemployment(negative) t +

β3*ΔUnemployment(negative) t-1 + ε t

where ΔArticles is the difference in the number of articles published in NRC Handelsblad

about unemployment and |αi| should be less than 1 so the time-series is stationary,

ΔΔUnemployment is the difference in the indicator of the differenced unemployment rate, α0

is the constant of the model and ε is the error term. The first model test for the simple

symmetric effect of changes in unemployment on the number of articles, while the second

model makes a difference between positive and negative changes in unemployment rate, to

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test whether those have different effects. The models take lag one to four into account,

because the general model with the dependent variable being lagged only once, showed

considerable autocorrelation, just as in the ADL models. Table 3 presents the coefficients of

both the symmetric and the asymmetric model.

Table 3. Error Corrections Models: unemployment rate and news coverage

 General model

(symmetric)General model (asymmetric)

Dead Start model (symmetric)

Dead Start model (symmetric)

Articles t-1 -.670** -.666** -.672** -.671**(.041) (.042) (.041) (.041)

Articles t-2 .134** .132** .135** .132**(.044) (.043) (.043) (.043)

Articles t-3 .083* .079* .083* .084*(.044) (.044) (.043) (.043)

Articles t-4 .123** .129** .125** .135**(.041) (.0425) (.041) (.042)

ΔΔUnemployment t -1.949(2.165)

ΔUnemployment t-1 -4.546 -2.788(2.907) (2.153)

ΔΔUnemployment(positive) t 1.754 -7.064*

(4.686) (4.027)

ΔUnemployment(positive) t-1 -6.708(4.725)

ΔΔUnemployment(negative) t -4.586(4.160)

ΔUnemployment(negative) t-1 -2.288 1.147

(4.890) (3.801)

Constant 4.338** 4.461** 4.340** 4.510**(.670) (.685) (.670) (.683)

Ljung-Box Q(20) residuals 22.86 24.82 21.95 24.44

Ljung-Box Q(20) residuals² 16.62 17.03 17.04 18.05

R2 / Adjusted R2 0.322 / 0.315 0.325 / 0.315 0.321 / 0.315 0.323 / 0.316Note. Cells contain OLS unstandardized regression coefficients with standard errors in parentheses;

* p < .10, ** p < .01

Again and logically, both models have almost an equal fit; they both explain about one third

of the variance in the difference of the number of articles that are published every week.

However, the model fit is different than those found with ADL models; ECM models explain

about 5% more variance of the number of articles. There are two more differences in these

findings compared with the results found with the ADL models: now there is not any effect of

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unemployment significant; and, the coefficient of the first lag of the dependent variable is

negative. As the (differenced) contemporary effects again are not significant and for the same

reason as mentioned above, it was appropriate to make the model more parsimonious by

constraining those to be zero. This creates a Dead Start Error Correction Models, which

makes it possible to compare the results with the findings of the ADL models (see Table 3 for

the coefficients).

In the symmetric Dead Start model, unemployment again had no significant effect;

conversely, the effect of positive changes in unemployment (when it increases) became

significant, just as in the ADL model. An increase of the unemployment by one percent,

would lead to about seven articles less being published in the next week. Following the results

form the Dead Start models, the difference in the number of articles can be defined as this for

the symmetric model:

ΔArticles = 4.340 + -.672*Articles t-1 + .135*Articles t-2 + .083*Articles t-1 + .125*Articles t-4 +

-2.788*ΔUnemployment t-1 + ε t

And the asymmetric Dead Start model looks like this:

ΔArticles = 4.510 + -.671*Articles t-1 + .132*Articles t-2 + .084*Articles t-1 + .135*Articles t-4 +

-7.064*ΔUnemployment(positive) t-1 + 1.147*ΔUnemployment(negative) t-1 + ε t

Those models are almost exactly the same as the models obtained via the ADL model; they

differ only on the coefficient for the first lag of the number of articles about unemployment.

Calculating by hand also leads to the same long run multipliers (LRM) for both models as

found for the results of the ADL models. Therefore, it is not necessary to describe them here

again. That the results are the same, once again proves the equivalence of both models; and,

thus also the claim of De Boef and Keele (2008) that ADL and ECM can be used for the same

data and that the choice for one of both depends on the coefficients that you want to calculate

directly.

ConclusionThis study has found that changes in the unemployment rate do not have an effect on the

number of articles being published about unemployment. This effect is insignificant in all

symmetric models that were studied. Therefore, the first hypothesis needs to be rejected. The

second hypothesis expected that negative changes in the unemployment rate have a stronger

effect on the number of articles being published about unemployment than the effects of

positive changes. Asymmetric models were used to study the difference between both effects.

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The hypothesis was confirmed, positive changes (when the unemployment increased) indeed

had a stronger effect than negative changes. However this effect was negative, meaning that

increases in unemployment in the Netherlands, lead to decreases in Dutch newspaper

coverage. This is opposite to the expectation and also contrary to the results of Soroka (2006).

How this can be explained is a good question for further research.

Reference

De Boef, S., & Keele, L. (2008). Taking time seriously. American Journal of Political

Science, 52(1), 184-200.

Hollanders, D., & Vliegenthart, R. (2009). The Influence of Negative Newspaper Coverage on

Consumer Confidence: The Dutch Case, CentER Discussion Paper Series (Vol. 2009).

Tilburg: University of Tilburg.

Soroka, S. N. (2006). Good news and bad news: Asymmetric responses to economic

information. Journal of Politics 68(2), 372-385.

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Do File:

*Left rightdrop if yrwk<199002drop if yrwk>200051

* declare data to be time seriesreplace nr2 = nr2 + 898tsset nr2, weekly

codebook leftrightcodebook N_BREAK

*Missing values, leftright is average of the two points coming before and after, articles is 0 as it means there were no articles about unemploymentreplace leftright= (leftright[_n-1]+leftright[_n+1])/2 if leftright>= .replace leftright= (leftright[_n-1]+leftright[_n+2])/2 if leftright>= .replace N_BREAK = 0 if N_BREAK>= .replace unumpl_rate = (unumpl_rate[_n-1]+unumpl_rate[_n+3])/2 if unumpl_rate>= .replace unumpl_rate = (unumpl_rate[_n-1]+unumpl_rate[_n+2])/2 if unumpl_rate>= .replace unumpl_rate = (unumpl_rate[_n-1]+unumpl_rate[_n+1])/2 if unumpl_rate>= .replace unumpl_rate = (unumpl_rate[_n-1]+unumpl_rate[_n+4])/2 if unumpl_rate>= .replace unumpl_rate = (unumpl_rate[_n-1]+unumpl_rate[_n+5])/2 if unumpl_rate>= .replace unumpl_rate = unumpl_rate[_n-1] if unumpl_rate>= .codebook unumpl_rate leftright N_BREAK

twoway (tsline N_BREAK, lcolor(black))twoway (tsline unumpl_rate, lcolor(black))

gen diff_unempl_rate = d.unumpl_ratetwoway (tsline diff_unempl_rate, lcolor(black))gen minus_unempl_rate = 0replace minus_unempl_rate = diff_unempl_rate if diff_unempl_rate<=0gen plus_unempl_rate = 0replace plus_unempl_rate = diff_unempl_rate if diff_unempl_rate>=0

*with driftdfuller N_BREAK*random walkdfuller N_BREAK, noconstant*trenddfuller N_BREAK, trend

*with driftdfuller diff_unempl_rate*random walkdfuller diff_unempl_rate, noconstant*trenddfuller diff_unempl_rate, trend

*with driftdfuller minus_unempl_rate *random walkdfuller minus_unempl_rate, noconstant*trenddfuller minus_unempl_rate, trend

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*with driftdfuller plus_unempl_rate *random walkdfuller plus_unempl_rate, noconstant*trenddfuller plus_unempl_rate, trend

twoway (tsline d.N_BREAK, lcolor(black))twoway (tsline d.unumpl_rate, lcolor(black))twoway (tsline minus_unempl_rate, lcolor(black))twoway (tsline plus_unempl_rate, lcolor(black))

*with driftdfuller d.N_BREAK*random walkdfuller d.N_BREAK, noconstant*trenddfuller d.N_BREAK, trend

dfuller d.unumpl_rate*random walkdfuller d.unumpl_rate, noconstant*trenddfuller d.unumpl_rate, trend

*most general ADL modelregress N_BREAK l.N_BREAK l2.N_BREAK l3.N_BREAK l4.N_BREAK diff_unempl_rate l.diff_unempl_rate predict r, reswntestq r, lags(20)gen r_s = r*rwntestq r_s, lags(20)drop r r_s

regress N_BREAK l.N_BREAK l2.N_BREAK l3.N_BREAK l4.N_BREAK minus_unempl_rate l.minus_unempl_rate plus_unempl_rate l.plus_unempl_ratepredict r, reswntestq r, lags(20)gen r_s = r*rwntestq r_s, lags(20)drop r r_s

*Dead start modelregress N_BREAK l.N_BREAK l2.N_BREAK l3.N_BREAK l4.N_BREAK l.diff_unempl_rate predict r, reswntestq r, lags(20)gen r_s = r*rwntestq r_s, lags(20)drop r r_s

regress N_BREAK l.N_BREAK l2.N_BREAK l3.N_BREAK l4.N_BREAK l.minus_unempl_rate l.plus_unempl_ratepredict r, reswntestq r, lags(20)gen r_s = r*rwntestq r_s, lags(20)drop r r_s

********************

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*ECM*general modelsregress d.N_BREAK l.N_BREAK l2.N_BREAK l3.N_BREAK l4.N_BREAK d.diff_unempl_rate l.diff_unempl_rate predict r, reswntestq r, lags(20)gen r_s = r*rwntestq r_s, lags(20)drop r r_s

regress d.N_BREAK l.N_BREAK l2.N_BREAK l3.N_BREAK l4.N_BREAK d.minus_unempl_rate l.minus_unempl_rate d.plus_unempl_rate l.plus_unempl_ratepredict r, reswntestq r, lags(20)gen r_s = r*rwntestq r_s, lags(20)drop r r_s

*Dead Startregress d.N_BREAK l.N_BREAK l2.N_BREAK l3.N_BREAK l4.N_BREAK l.diff_unempl_rate predict r, reswntestq r, lags(20)gen r_s = r*rwntestq r_s, lags(20)drop r r_s

regress d.N_BREAK l.N_BREAK l2.N_BREAK l3.N_BREAK l4.N_BREAK l.minus_unempl_rate l.plus_unempl_ratepredict r, reswntestq r, lags(20)gen r_s = r*rwntestq r_s, lags(20)drop r r_s

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