Journal of International Fisheries
vol.16，2018▶Article ◀

Consumers’ Attitude Toward Inspection Methods and Institutions for Potential
Radioactive Contamination: A Choice-based Conjoint Analysis
Yutaro SAKAI†, Akira NAKAMURA＊, Nobuyuki YAGI, Takashi SUZUKI,
Taro OISHI＊＊ and Hisashi KUROKURA＊＊＊（The University of Tokyo, Graduate School／＊Otsuchi Town Government／
Fukuoka Institute of Technology／＊＊＊Hunet ASA）＊＊

E-mail：†ytr.sakai@gmail.com【abstract】
Japanese fisheries suffered substantial damages from the tsunami in March 2011. The
subsequent accident at the Fukushima nuclear power plant raised serious concerns
among consumers about the potential contamination of fishery products by radioactive
substances. Inspections for radioactive contamination has been conducted since then,but it is not clear whether the current practice is the most desirable one. In this paper,
we employ a choice-based conjoint analysis using data from online survey conductedduring August 21-23, 2012 to examine how consumers evaluate the inspection methods
and inspection institutions for fishery products, and how providing information may
change their evaluation. We find that consumers have a very high evaluation for full
(100%) inspection for radioactive contamination for salmon (rather than sample
inspection), which does not change after providing two different sets of information. We
also find that consumers prefer universities and fishery cooperatives to government
institutions as an inspection institution. This evaluation is, however, reversed after
providing scientific information about radioactive contamination. Further, our result
indicates that providing information about how local producers are suffering does notchange consumers’ evaluation. These results suggest that the inspection for all
marketed products, together with effective communications to consumers, are crucial
in dealing with potential radioactive contamination.

【keywords】
conjoint analysis, consumer attitudes, Fukushima, radioactive contamination, salmon

1. Introduction
Japanese fisheries suffered substantial damages from the earthquake and- 19 -

Yutaro SAKAI, Akira NAKAMURA, Nobuyuki YAGI, Takashi SUZUKI,
Taro OISHI and Hisashi KUROKURA

subsequent tsunami in March 2011. The tsunami not only physically damaged fishingvessels and ports in northeastern areas of Japan, it also raised serious concerns among
consumers about the risk of potential radioactive contamination of fishery products
following the accident at the Fukushima nuclear power plant (Ito et al. (2011)). Allcommercial fishing activities in Fukushima waters were suspended from March 2011
to June 2012 (Yagi (2014)). Limited fishing operations has restarted since June 2012 as“trial operation” under close supervision of the government and fisheries organizations,and the amount of landing in 2015 is still around 1/30th of that harvested by commercial
fisheries before the disaster (Yagi (2016)).
Concerns among consumers were reported in newspapers and other media regarding
the quality and frequency of inspections for radioactivity. For instance, the Kahoku
Shimpo, one of the major newspaper based in tsunami damaged area, reported in its
article on 7 September 2013 about an incident: a retailor in Fukushima sold a fish to acustomer, but the fish was returned to the store the next day by the consumer who
claimed that her family raised a concern on this product. This kind of concern is unlikely
to be unique to the Fukushima nuclear plant accident. As such, we believe it isimportant to know how consumers evaluate inspection methods and inspection
institutions for radioactive contamination. It is also crucial from policy perspectives toknow what kind of information, if any, changes their evaluation.
There is a large literature examining consumer’s risk preference and attitude towardvarious products. Many studies find that consumers give premiums for inspected orcertified food (e.g., McCluskey et al. (2005), Wang et al. (2009), Chalak and Abiad(2012)). However, to the best of our knowledge, there is no study that examines theconsumers’ evaluation for inspection methods. Alternatively, there is a few studies thatexamine inspection institutions. Holland and Wessells (1998) show that consumers in
the north-eastern and mid-Atlantic states in the United States prefer United States
Department of Agriculture (USDA) to Food and Drug Administration (FDA) as anagency for seafood safety and quality inspection. Ortega et al. (2011) show that Chinese
consumers have higher willingness to pay for pork with a government certification
program than third-party certification. In a somewhat different context, Wessells,
Johnston and Donath (1999) find that consumers are indifferent among the World Wide
Fund for Nature (WWF), the Marine Stewardship Council (MSC), and National Marine
Fisheries Service (NMFS) as a certifying agency for an eco-labels. Thus, our study isthe first to analyze the consumers’ evaluation for inspection agency (and methods) inthe context of radioactive contamination.
- 20 -

Consumers’ Attitude Toward Inspection Methods and Institutions for Potential Radioactive
Contamination: A Choice-based Conjoint Analysis

Another related set of studies show that providing information can potentially change
consumers’ behaviors. For instance, Uchida et al. (2014) use an auction experiment toshow that consumers give about a 20 percent premium for a MSC certified salmon only
if they are provided information on both the status of global fish stocks and the goal of
the MSC programs. In contrast, Miyata and Wakamatsu (2015) also use an auction
experiment

to

find

that

providingscientificinformation

about

radioactive

contamination does not affect consumers’ willingness to pay for wakame seaweed; itmerely affects their perceptions about radioactive contamination. We contribute to thisliterature by testing the effect of a unique information set. Specifically, in addition toscientific information, we also test the effect of providing local information about how
producers are suffering from decreased prices. We do not find any research that
implement a similar information treatment.
We use a choice-based conjoint analyses in this study, which has already been applied
for Japanese seafood market by several authors. The first application appears to be
Ariji (2006) that examines consumers’ evaluation for flounder harvested in Kyoto
prefecture. More recently, Oishi et al. (2010) and Uchida et al. (2014) both focus on how
consumers evaluate ecolabels for sliced salmon in Japan. Ariji (2010) also investigates
the impact of product type and ecolabels for Bluefin tuna. We follow their study designand compare our results with theirs if possible.
The rest of the paper proceeds as follows. In Section 2, we describe the designs forour survey and choice experiments. In Section 3, we explain the conceptual framework
behind our conjoint analysis, and describe four alternative econometric specifications.
Section 4 includes estimation results and the willingness to pay for each attributederived from the results. Finally, in Section 5, we discuss the interpretation and policy
implications.

2．Survey design
We conducted our online survey during August 21-23, 2012 under the title “Thesurvey for seafood products.” It consists of four parts that include 39 questions in total.
The first part includes general questions about the respondent’s attitudes towards fishconsumption and their familiarity with several fish species. In the second part, we firstprovide basic information about the inspection methods for radioactive contamination,and then conduct five choice experiments. In the third part, we randomly divide therespondents into two groups and provide scientific information about radiation to one- 21 -

Yutaro SAKAI, Akira NAKAMURA, Nobuyuki YAGI, Takashi SUZUKI,
Taro OISHI and Hisashi KUROKURA

group while the information about the local situation in the affected areas to the othergroup. Five choice experiments are conducted again after the new information isprovided. Finally, the survey closes with questions about the demographic informationof the respondents.
To quantify the consumers’ evaluation for inspection methods and institutions, weneed to determine the focus product that is used for the choice experiments. We selectsliced salted salmon (two pieces, 160 gram) shown in Fig.1 for three reasons. First,
sliced salmon is one of the most popular fishery products sold in Japan and is therefore
easily recognizable to respondents. Second, it is a major farmed fishery product in thearea affected by the 2011 tsunami. Finally, although Coho salmon was never reported
to be contaminated, it faced a major decrease in ex-vessel price after the Fukushima
nuclear power plant accident. This decrease was mainly driven by imported Cohosalmon from Chile(1), but we cannot entirely exclude the possibility that the demand forthe domestic Coho salmon decreased due to the concern for radioactive contamination.
Thus, Coho salmon seems to be a good subject to examine whether providing new
information to respondents changes their product evaluation.
We contracted out our online questionnaire survey to Macromill, Inc., an internet
research company based in Tokyo, Japan. The questionnaires were designed by theauthors, and Macromill distributed them to a prospective pool of respondents. The
respondents are pre-registered Japanese residents, whose identities are known toMacromill. By answering questionnaires, the respondents can earn “points” which areexchangeable for gifts in several stores. A total of 840 people was surveyed, which
consists of 21 people from each combination of two genders (male and female), fivecohorts (20-29, 30-39, 40-49, 50-59, and 60-), two areas (Tokyo and Osaka), and two
information treatments (A and B). Following Oishi et al. (2010), we selected Tokyo andOsaka, which are two major seafood consumption areas in Japan.

Figure 1 Picture of salmon product subject to study- 22 -

Consumers’ Attitude Toward Inspection Methods and Institutions for Potential Radioactive
Contamination: A Choice-based Conjoint Analysis

2-1．Product attributes and levels
Although our primary interest is the consumers’ evaluation for the inspection
methods and institutions, a sliced salted salmon has number of other attributes. To
uncover the consumers’ preference, it is desirable to include in the choice experiments
other key attributes to mimic the actual purchasing situations. As such, we include
three other attributes following previous studies: price, product type, country or area oforigin. In terms of price, we assume four price levels for two pieces of salmon based on
the actual retail price: 150 yen, 200 yen, 300 yen, and 400 yen. These price levels arealso consistent with those employed by Oishi et al. (2010) and Uchida et al. (2014). As
for the product type, wild and farmed are considered as two options. Regarding thecountry or area of origin, we assume four possibilities: Miyagi (tsunami-affected area
located next to Fukushima), Hokkaido (far northern area of Japan with minimal
tsunami damage), Chile, or Norway. Although previous studies do not distinguishamong production areas in Japan, we treat Miyagi and Hokkaido as separate areas. As
Miyagi is much closer to Fukushima, it is possible that consumers evaluate products
from these areas quite differently.
The inspection method is specified as either sample inspection or full (100%)
inspection(4). Sample inspection refers to the inspection of randomly selected samples
using a germanium semiconductor detector, and has been under implementation since
January 2013. This method takes a long time due to the large number of requests forinspections being received by the limited number of inspection institutions in Japan. It
also requires fish samples to be grinded and, as such, the inspected products cannot besold on the market even if they turn out to be free of radioactive contamination. On theother hand, a new equipment was developed in 2012 that can measure the level ofradioactive substances contained in the whole fish in 10 seconds without grinding it.
This equipment looks like an airport security machine for scanning carry-on luggage.
Fish products within a box are placed on a belt conveyer and the level of radioactive
contamination is measured while the fish passes under the sensor. Because it does not
require the grinding of the fish, this type of full inspection for marketed fish istheoretically feasible. In this study, full inspection is defined as the inspection of all
marketed products using the belt conveyer method. This information is given to the
respondents, along with the explanation that cross-checking of the level ofcontamination would be conducted using germanium semiconductor detector devices
for selected samples to standardize the accuracy of the measurement by the twodifferent types of devices.
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Yutaro SAKAI, Akira NAKAMURA, Nobuyuki YAGI, Takashi SUZUKI,
Taro OISHI and Hisashi KUROKURA

Table 1 Product attributes and levels
Attribute

Level

Price

150 yen, 200 yen, 300 yen, 400 yen

OriginMiyagi, Hokkaido, Chile, Norway.

Product type

Farmed, Wild

Inspection method

Full (100%) inspection, sample inspection

Inspection institution

Government, Fishery cooperative, Universities, Consumer

We consider four potential inspection institutions: government agencies, fisherycooperatives, universities, and consumers’ self-inspection. After the accident at thenuclear power plant in Fukushima, various institutions have been involved in theinspection of seafood products. Government agencies at national and prefectural levels
are playing major roles in inspection, but the number of inspectors and inspection
machines are currently unable to meet the large demand for such inspections.
University research laboratories voluntarily help to analyze the level of radioactive
substances included in the seafood products. In addition, fishery cooperatives are also
engaged in similar inspections to maintain accountability towards their customers. The
summary of product attributes and levels are shown in Table 1.
Given the number of attributes and levels, the possible number of profile sets is 4 x
4 x 2 x 2 x 4 = 256. To reduce the burden of the respondents, however, we assume that
there is no interaction effect among attributes/levels, and use the L16 orthogonal tableto create 16 profile sets. One profile set was further dropped due to its unrealistic
combination of profiles: Chile, farmed, sample inspection, government agency, and 400
yen(2). This results in the total of 15 profile sets, which then allows us to create fivechoice experiments, each containing three alternatives. By randomly shuffling the 15
profile sets, we create 10 choice experiments No.1 - No.10. The respondents answer
choice experiments No.1 - No.5 after receiving the basic information, while they answer
choice experiments No.6 - No.10 after receiving the new information. In each choice
experiment, respondents are asked to choose one of four alternatives, three profile sets
and a “None of the above” option.
2-2．Information treatment
Prior to the initial choice experiments, we provide to all the respondents basic
information that clarifies the definitions of and the difference between sample
inspection and full inspection. This procedure ensures that respondents accurately- 24 -

Consumers’ Attitude Toward Inspection Methods and Institutions for Potential Radioactive
Contamination: A Choice-based Conjoint Analysis

Table 2 Content of information treatment
1.

Sample inspection is such that randomly selected samples at landing
ports are sent to research institutes and tested. The level ofradioactive substances is measured using germanium semiconductor
detectors. This method requires fish to be grinded up, and, as such theinspected products cannot be sold on the market. It usually requires 2
or 3 days before the results can be obtained from research institutes.

2.

Full (100%) inspection is such that fish products are placed on a belt
conveyer and the level of radioactive contamination is measured while
the fish is passing under the sensor. It takes 10 seconds without
grinding the fish. Because it does not involve a process for fish to be
grinded, full inspection for marketed fish is theoretically feasible.

3.

In the questionnaire, full inspection is defined as the inspection for all
the marketed products using the belt conveyer method. Full inspection
involves cross checking the level of contamination with germanium
semiconductor detector devices for selected samples to standardize theaccuracy of the measurement by two different types of devices.

1.

Radioactive substances naturally exist in food and our atmosphere.
The Codex Commission set standards on acceptable levels ofradioactive Cesium 134-137. The most recent regulations in Japan are
fully consistent with this standard.

2.

Sample inspection method does not exclude the possibility that somemarketed fish contains radioactive substances above the criteria.
However, it is extremely unlikely that one consumer purchases such afish repeatedly. The total yearly intake of radioactive substances
would still be reasonably lower than the allowable level, even if a
consumer inadvertently purchases contaminated fish.

1.

The price of farmed Coho salmon in Miyagi Prefecture has dropped tohalf of the average price in past years.

2.

Producers in Miyagi say that “we have tried hard to recover from thetsunami, but our efforts cannot be sustained under this situation.”3.

JF Miyagi is appealing that the “feed materials and environment tofarmed salmons are free of radioactive substances”, “productinspections are rigorously conducted”, and that “the tsunami-damaged
Miyagi salmon farming industry cannot be sustained without supports
from consumers through actual consumption behaviors.”

Basic
Information

Information
set A

Information
set B

recognize their trade-offs, which is crucial in uncovering their preference towardvarious attributes. In addition, providing the basic information to respondents makes
it more credible that they accurately understand the new information we provide after- 25 -

Yutaro SAKAI, Akira NAKAMURA, Nobuyuki YAGI, Takashi SUZUKI,
Taro OISHI and Hisashi KUROKURA

the initial choice experiments. A caution is required, however, because after providing
the basic information, our sample is no longer a representative sample of the population.
Our results can only be extended to the general population conditional on providing thebasic information.
After the first set of choice experiments, the participants are randomly divided into
two groups, each of which is offered a different set of information A or B. Information
Set A is about the risk management action, which is taken from the websites of theConsumer Affairs Agency of Japan and independent scientific institutions. It explainsthat radioactive materials exist in nature independent of the nuclear power plant
accident. It also states that the regulation criteria for radioactive contamination is set
following inter-governmental organization guidelines, and that the radiation level isunlikely to exceed the permissible level unless one repeatedly consumes a contaminatedfish by chance.
Information set B is based on newspaper articles which describes the state of the
producers in Miyagi in 2012. It states that the producers are suffering from decreased
prices despite that their products are shown to be radioactive free, and that they needsupport from consumers to make their living. The difference between Information sets
A and B is that the former provides objective and scientific information about
radioactive contamination, while the latter conveys information about local situationsin an emotional manner. The summary of the basic information, Information set A, andInformation set B are given in Table 2.

3．Conceptual framework and econometric model
We conduct a conjoint analysis using the results from the choice experiments. It is
assumed that consumers make their purchasing decision by comparing utilities
obtained from the combination of product attributes. Denote the utility for an individual
consumer n from option i at choice experiment t as:
𝑈𝑛𝑖𝑡 = 𝑉𝑛𝑖𝑡 + 𝑒𝑛𝑖𝑡
where 𝑉𝑛𝑖𝑡 is the utility from observable product attributes and 𝑒𝑛𝑖𝑡 is theunobservable component of utility. This unobservable component includes utility fromunmeasured characteristics of the product and other idiosyncratic shocks such as theconsumer’s mood and physical conditions. Given a choice set C, the probability of theconsumer choosing option i is given by:- 26 -

Consumers’ Attitude Toward Inspection Methods and Institutions for Potential Radioactive
Contamination: A Choice-based Conjoint Analysis

Pr(𝑈𝑛𝑖𝑡 > 𝑈𝑛𝑗𝑡 ) = Pr(𝑉𝑛𝑖𝑡 − 𝑉𝑛𝑗𝑡 > 𝑒𝑛𝑗𝑡 − 𝑒𝑛𝑖𝑡 )∀𝑗 ∈ 𝐶, j ≠ iThus, if we specify a functional form for the observed component V and assume aprobability distribution for the unobservable component of utility e, the probability ofchoosing option i can be expressed in terms of observable attributes.
We assume that attributes linearly enter the observed component of utility. We
employ dummy coding and use the following base categories: Norway, farmed, sample
inspection, and consumer self-inspection. Thus, the explanatory variables in ourestimation are price, three country of origin dummies (Hokkaido, Miyagi, and Chile),
wild dummy, full inspection dummy, three inspection institution dummies (University,
Fishery cooperative, and Government), and the common alternative specific constantfor choice 1-3. Further, to assess the effect of information treatments, we include
interaction terms of these variables with the information A and information B dummy
variables. Thus, our base specification includes 30 explanatory variables in total. The
magnitude of each parameter estimates will be evaluated by the marginal willingness
to pay (MWTP), which is calculated as the price change that offsets a unit change in
the attribute while keeping the total utility constant.
As for the unobservable component, we employ four alternative specifications andexamine the robustness of our results. The first specification is the usual conditional
logit specification where the unobservable component is assumed to follow the iid TypeI extreme value distribution.
𝑈𝑛𝑖𝑡 = 𝑿′𝒏𝒊𝒕 𝜷 + 𝑒𝑛𝑖𝑡 , 𝑒𝑛𝑖𝑡 ~ 𝑖𝑖𝑑 𝐺(0,1)
where 𝑿′𝒏𝒊𝒕 is a vector of explanatory variables. In this specification, the choiceprobability has a closed form solution so that the estimation is relatively simple. The
assumption of the iid Type-I extreme value distribution, however, implies theindependence from irrelevant alternatives (IIA), which states that the odds of choosing
between two alternatives is independent of other alternatives. This is a quite restrictive
assumption to make for studies that use observational data, because unmeasured
characteristics of each product are likely to exist (which makes some alternatives closer
substitutes than others). In our study, however, this assumption seems more innocuous
because our data is generated from choice experiments, where there is no unmeasured
characteristics in principle. A potential concern is that IIA implies that unobservable
components of utility across 10 choice experiments by the same respondent are
independent. However, if a respondent is in a bad mood in the first choice experiment,
it is likely that he/she is in the same mood until the last choice experiment (which- 27 -

Yutaro SAKAI, Akira NAKAMURA, Nobuyuki YAGI, Takashi SUZUKI,
Taro OISHI and Hisashi KUROKURA

results in a correlation between e for the same person over choice experiments).
To deal with these concerns, we estimate three other models that do not require IIA:
multinomial probit model, nested logit model, and mixed logit model. In a multinomial
probit model, the unobservable components of utility are assumed to be distributed
jointly normal. With four alternatives in each choice experiment, there are 10 elements
to estimate in the covariance matrix. By removing parameters related to scale and levelof utilities, the number of parameters to be estimated reduces to five (Train (2007)).
Thus, the multinomial probit model in our analysis has five additional parameters.
𝑈𝑛𝑖𝑡 = 𝑿′𝒏𝒊𝒕 𝜷 + 𝑒𝑛𝑖𝑡 , 𝑒𝑛𝑖𝑡 ~ 𝑀𝑉𝑁(0, 𝛺)In our nested logit model, we assume that the respondents first decide whether topurchase or not, and conditional on deciding to purchase, they choose among the three
profile sets (Haaijer et al. (2001)). Thus, we model three profile sets in the first nest
while the “None of the above” option in the second nest. It is assumed that IIA holds
within the first nest. We have one additional parameter to estimate (i.e., dissimilarity
parameter), which measures the degree of independence among unobserved
components of utility for the three alternatives in the second nest. The utility function
is given by
𝑈𝑛𝑖𝑡 = 𝑊𝑛𝑘 + 𝑿′𝒏𝒊𝒕 𝜷 + 𝑒𝑛𝑖𝑡 , 𝑒𝑛𝑖𝑡 ~ 𝑖𝑖𝑑 𝐺(0,1)
where 𝑊𝑛𝑘 is the common utility from alternatives in the nest k.
Finally, in a mixed logit model, potential heterogeneity in preference acrossrespondents can be modelled by treating some parameters to be random. We specify theprice parameter as fixed while other nine parameters are distributed normal. All theinteraction terms are also assumed to be fixed due to the computational complexity.
𝑈𝑛𝑖𝑡 = 𝑿′𝒏𝒊𝒕 𝜷𝒏 + 𝑒𝑛𝑖𝑡 , 𝑒𝑛𝑖𝑡 ~ 𝑖𝑖𝑑 𝐺(0,1)
We use likelihood ratio (LR) tests to determine the preferred model between theconditional logit and the nested logit models, and between the conditional logit andmixed logit models. As multinomial probit is not nested with any other model, Akaike
Information Criterion (AIC) and Bayesian Information Criterion (BIC) are used tomake comparison.

4．Results
We collected data from 840 people in total. As designed, it consists of 21 people fromeach city, gender, cohort, and information treatment. Their other demographic- 28 -

Consumers’ Attitude Toward Inspection Methods and Institutions for Potential Radioactive
Contamination: A Choice-based Conjoint Analysis

characteristics are as follows: 37% of them are full-time company employees, 21% are afull-time housewives/husbands, and 13% are part-time workers. 23% of the respondents
have the annual household income of 4-6 million yen, followed by 22% having thehousehold income of 2-4 million yen. In terms of the highest educational level completed,
45% have a university degree, 21% have a college degree, and 27% have a high school
degree. Regarding their attitude towards seafood consumption, 78% of the respondents
answered that they liked to eat fish, and more than half of the respondents consumed
fish two days or more per week. 17% of the respondents indicated that they had previous
knowledge about the inspection methods for radioactive materials explained in ourquestionnaire.
The number of observations for our conjoint analysis is 33600 (= 840 x 10 x 4). To
account for the differential demographic composition of our sample relative to the
population in Japan, we used the inverse probability weighing by age class and genderin each city, based on the population data in 2012 estimated by Statistics Bureau.
Estimations were conducted using Stata 12. Columns 1-4 in Table 3 show the resultsfrom the conditional logit, multinomial probit, nested logit, and mixed logit models,
respectively(3). Although not shown in the table due to the space limitation, three out offive parameters for the covariance matrix are statistically significant in themultinomial probit model, the dissimilarity parameter is significantly different from
one in the nested logit model, and the standard deviations for the random parameters
are all significant for the mixed logit model.
When the four columns are compared, they show overall consistent results in termsof the signs of the parameter estimates. No parameter exhibits statistically significant
estimates with opposite signs across the four columns. We view that those parametersthat are statistically significant with the same sign across the four columns are ourmost robust results. As for the main effects, the four models agree that Miyagi andChile are less preferable to Norway, wild salmon is more preferred to farmed salmon,
full inspection is preferable to sample inspection, universities and fishery cooperatives
are better than consumers’ self-inspection, and a lower price is desirable. Regarding
interaction terms, the four models agree that providing Information A raises consumers’
evaluation for Chilean salmon, but decreases their evaluation for universities andgovernments as an inspection institution. Alternatively, they agree that providing
Information set B raises consumers’ evaluation for Chilean salmon.
There are also some differences across the four models. First, the conditional logit
model indicates that Hokkaido salmon is indifferent with Norwegian salmon for- 29 -

Yutaro SAKAI, Akira NAKAMURA, Nobuyuki YAGI, Takashi SUZUKI,
Taro OISHI and Hisashi KUROKURA

consumers, while the other three models suggest that Hokkaido salmon is preferable to
Norwegian salmon. Second, the conditional logit and the mixed logit suggest thatgovernment agencies are preferable to consumer self-inspection, while the other twomodels suggest these two options are indifferent. Third, the conditional logit, themultinomial probit, and the nested logit indicate that providing either Information set
A or B raises consumers’ evaluation for Miyagi salmon. However, the mixed logit model
suggests this is not the case. Finally, the conditional logit model indicates that providing
either information reduces their evaluation for full inspection relative to sample
inspection, but the other three models do not agree with it.
We choose the mixed logit model as our preferred model based on the log likelihood,
AIC, and BIC: LR tests reject the hypothesis that the conditional logit is preferable tothe nested logit (p<0.000) and to the mixed logit model (p<0.000), and AIC and BIC
suggests the mixed logit is preferable to the multinomial probit and the nested logit
models. Therefore, our main results, in addition to the ones listed above, are as follows.
First, Hokkaido salmon is preferable to Norwegian salmon. Second, government
agencies are preferable to consumer self-inspection. Third, the negative evaluation for
Miyagi salmon does not change with Information set A or B. Finally, the consumers’
evaluation for full inspection is not affected by Information set A or B.
Column 5 and 6 in Table 3 show the mixed logit estimation results for Tokyo andOsaka, respectively(5). Although our aim in this paper is to examine the consumers’
evaluation for inspection methods and institutions on average, it is of some interest to
see if there is any regional difference in their evaluation. Given that Tokyo is muchcloser to Fukushima, and that there are differences in the consumption of various fish
products between these two areas, it is plausible that their evaluation for inspection
methods and institutions may also differ. The estimation results suggest that the twocities have overall consistent preference toward various attributes, as almost all theparameter estimates have the same sign across two columns. There are, however, somenotable differences in terms of statistical significance. First, Miyagi salmon isindifferent with Norwegian salmon in Tokyo, but it is less preferable in Osaka. This isconsistent with Aruga (2016) that shows more distant consumers require a higher
discount rate to accept agricultural products from regions near the Fukushima nuclear
plant. Further, when Information set A is provided, consumers’ evaluation for Miyagi
salmon does not change in Tokyo, but it earns even worse evaluation in Osaka. Second,
full inspection is preferred in both cities, but when Information set A is provided, it- 30 -

Consumers’ Attitude Toward Inspection Methods and Institutions for Potential Radioactive
Contamination: A Choice-based Conjoint Analysis

Table 3 Estimation results
ASC
ASC x infoA
ASC x infoB
Hokkaido
Hokkaido x infoA
Hokkaido x infoB
Miyagi
Miyagi x infoA
Miyagi x infoB
Chile
Chile x infoA
Chile x infoB
Wild
Wild x infoA
Wild x infoB
Full inspection
Full inspection x infoA
Full inspection x infoB
University
University x infoA
University x infoB
Fishery coop
Fishery coop x infoA
Fishery coop x infoB
Government
Government x infoA
Government x infoB
Price
Price x infoA
Price x infoB
N
LL
AIC
BIC

CLogitAll
1.821***(0.186)-0.062(0.240)-0.116(0.242)0.121(0.135)0.300*(0.162)
0.396**(0.162)-0.709***(0.117)
0.586***(0.146)0.780***(0.146)-1.151***(0.112)
1.038***(0.159)1.109***(0.160)0.422***(0.142)-0.255*(0.153)-0.415***(0.154)0.653***(0.061)-0.262**(0.116)-0.199*(0.117)0.760***(0.132)-0.615***(0.162)-0.382**(0.164)
1.147***(0.123)-0.917***(0.152)-0.761***(0.153)0.774***(0.207)-0.428*(0.229)-0.280(0.230)-0.008***(0.001)0.002*(0.001)0.002*(0.001)33600-442701885463885716

MProbitAll
2.432***(0.607)-0.320(0.292)-0.344(0.288)0.284*(0.158)0.020(0.172)0.107(0.163)-0.496***(0.126)
0.392***(0.138)0.565***(0.137)-0.827***(0.125)0.696***(0.135)0.757***(0.143)0.469***(0.148)-0.254(0.161)-0.374**(0.168)0.430***(0.096)-0.008(0.160)0.069(0.169)0.427**(0.208)-0.425*(0.232)-0.271(0.227)0.870***(0.147)-0.715***(0.162)-0.615***(0.166)0.335(0.268)-0.194(0.292)-0.087(0.291)-0.007***(0.001)0.002*(0.001)
0.002(0.001)33600-442066
884202884497

NLogitAll
2.263***(0.215)-0.435*(0.236)-0.411*(0.221)0.366***(0.128)-0.017(0.160)0.044(0.164)-0.290**(0.133)0.270**(0.119)0.391***(0.133)-0.638***(0.180)0.697***(0.160)0.750***(0.161)
0.482***(0.104)-0.400***(0.115)-0.497***(0.110)0.258**(0.126)0.084(0.123)0.140(0.125)0.476***(0.130)-0.508***(0.118)-0.399***(0.105)0.733***(0.156)-0.662***(0.129)-0.601***(0.112)0.079(0.253)0.056(0.220)0.131(0.205)-0.007***(0.001)0.003***(0.001)0.003***(0.001)33600-442448884959885220MLogitAll
4.337***(0.460)0.288(0.367)0.357(0.388)1.381***(0.207)-0.923***(0.254)-0.802***(0.228)-0.332**(0.166)-0.229(0.188)-0.039(0.200)-1.206***(0.145)0.435**(0.198)0.515**(0.214)0.752***(0.186)-0.236(0.207)-0.489**(0.193)0.995***(0.104)-0.218(0.161)-0.156(0.178)1.051***(0.165)-0.772***(0.199)-0.429*(0.224)0.852***(0.146)-0.405**(0.185)-0.164(0.195)0.724***(0.264)-0.249(0.297)-0.153(0.289)-0.010***(0.001)0.000(0.002)0.000(0.001)33600-354088708255708583

MlogitTokyo
3.851***(0.596)0.276(0.503)0.453(0.547)1.058***(0.272)-0.558(0.343)-0.742**(0.313)-0.146(0.234)-0.047(0.237)-0.065(0.274)-1.216***(0.197)0.667**(0.268)0.641**(0.298)0.709***(0.238)-0.171(0.275)-0.321(0.249)1.075***(0.149)-0.051(0.205)-0.158(0.238)0.751***(0.226)-0.629**(0.266)-0.215(0.311)
0.633***(0.192)-0.332(0.256)-0.006(0.263)0.799**(0.348)-0.420(0.393)-0.162(0.380)-0.009***(0.002)-0.002(0.002)-0.002(0.002)16800-214510429098429399

MlogitOsaka
4.307***(0.642)0.404(0.580)0.411(0.542)
1.661***(0.307)-1.483***(0.352)-0.894***(0.323)-0.796***(0.273)-0.622**(0.290)0.114(0.286)-1.170***(0.211)
0.052(0.277)0.310(0.286)0.808***(0.291)-0.366(0.313)-0.722**(0.302)0.956***(0.160)-0.585**(0.268)-0.294(0.261)
1.448***(0.233)-0.897***(0.282)-0.692**(0.290)1.139***(0.220)-0.484*(0.250)-0.417(0.262)0.628(0.410)-0.060(0.441)-0.159(0.436)-0.011***(0.002)0.002(0.002)0.002(0.002)16800-138758277594277895

Notes: Clogit stands for conditional logit, MProbit multinomial probit, NLogit
nested logit, and MLogit mixed logit. The inverse probability weighing by
age class and gender in each city is used to account for different composition
between the sample and the population. * P<0.1, ** P<0.05, *** P<0.01- 31 -

Yutaro SAKAI, Akira NAKAMURA, Nobuyuki YAGI, Takashi SUZUKI,
Taro OISHI and Hisashi KUROKURA

Table 4 Marginal Willingness to Pay for each attribute
Base

InfoA

Diff

InfoB

Diff

Hokkaido141.39***46.91**

Yes

59.27***

Yes

Miyagi-33.96*-57.45***

Chile-123.48***-78.92***

Wild

77.04***

Full-37.97*
Yes-70.78***Yes

52.92***

26.92***

Yes

101.86***79.55***

85.91***

University

107.60***28.59**

Yes

63.70***Fish coop

87.27***

45.80***

Yes

70.45***

Government

74.09**

48.62***

58.44***

Notes: Diff shows whether the estimates are significantly different from the Baseestimates at the 10% level of significance. * P<0.1, ** P<0.05, *** P<0.01

becomes less important only in Osaka. Finally, government agencies are preferred inTokyo, but it is indifferent with consumer self-inspection in Osaka.
The MWTP calculated from the mixed logit model are shown in Table 4. All theestimates are significantly different from zero. Without providing new information,
consumers give a premium of 101 yen for full inspection and premiums of 107 yen, 87
yen, and 74 yen to universities, fisheries cooperatives, and government, respectively.
These are quite large numbers given that the price of the sliced salmon ranges between
150-400 yen. When Information set A is provided, the premium for full inspection
decreases by 20% to 79 yen, although the difference is not statistically significant. The
premiums for inspection institutions are also decreased. At the same time, however, anegative premium for Miyagi salmon increases from -33 yen to -57 yen (though, thedifference is not statistically significant). Providing Information set B has similar, but
smaller, effects: the premium for full inspection decreases to 85 yen, for inspection
institutions are all decreased, while the negative premium for Miyagi salmon increases.

5．Discussion
In this paper, we used a choice-based conjoint analysis to examine how consumers
evaluate inspection methods and inspection institutions for radioactive contamination,and how providing new information changes their evaluations. In the choice
experiments, we included other key attributes of the product to mimic the actual
purchasing situations, which also allows us to compare our results with those from- 32 -

Consumers’ Attitude Toward Inspection Methods and Institutions for Potential Radioactive
Contamination: A Choice-based Conjoint Analysis

previous studies. Knowing that different econometric models may generate different
results, we estimated four different models to ensure the robustness of our results.
Three main findings were obtained from our analysis. First, consumers have a very
robust and high evaluation for full inspection relative to sample inspection. Thisevaluation does not change, on average, even after providing information thatradioactive substances exist in the nature and the occasional consumption ofcontaminated seafood does not cause any health problem. Providing information about
how local fishermen suffer from reputational damages does not change this evaluation,either. The MTWP from the mixed logit model suggests that consumers are, on average,
willing to pay 101 yen for full inspection relative to sample inspection. Miyagi
prefecture has annual Coho salmon production of about 13,000 ton, which amounts to
13,000 * 0.7 * 1,000,000 / 160 = 56,875,000 packs of sliced salmon (assuming the yieldratio of 70%). Thus, full sampling is expected to raise an additional revenue of 101 *
56,875,000 =5.7 billion yen, which seems sufficiently high to cover the initial andrunning costs for the equipment for the entire Miyagi prefecture(6).
Second, as an inspection institution, universities and fishery cooperatives earn ahigher evaluation than governments. Although further research is needed, the lower
consumer evaluation for products inspected by government agencies may represent
their (relative) distrust in governments. The poor information disclosure regarding themagnitude of damages to the Fukushima nuclear power plant may have particularlyraised consumers’ distrust to the government. Interestingly, however, after providing
Information set A, consumers prefer government agencies rather than universities andfishery cooperatives. One possibility is that Information set A, which describes how thegovernment objectively set the criteria for radioactive contamination, may have raised
the relative evaluation for the government. In contrast, Information set B has limited
effect on the consumers’ evaluation for inspection institutions (and full inspection). It
appears that consumers are less affected by emotional and local information, and canbe more affected by scientific and objective information.
Finally, the parameter estimates for other characteristics are aligned with those inprevious studies. For example, our results show that Chilean salmon is less preferable
to Norwegian salmon, which is consistent with the findings in Oishi et al. (2010) and
Uchida et al. (2014). Also, we find that wild salmon is preferable to farmed salmon,
which is the same finding as Uchida et al. (2014). These consistencies indicate that theparameter estimates for inspection methods and inspection institutions in our study
are also reliable. In addition, we find that the evaluation for Hokkaido salmon and- 33 -

Yutaro SAKAI, Akira NAKAMURA, Nobuyuki YAGI, Takashi SUZUKI,
Taro OISHI and Hisashi KUROKURA

Miyagi salmon are dramatically different, with the former more preferred to Norwegiansalmon while the latter less preferred to it. This presumably reflects consumers’ lowlevel of confidence in the safety of food products from the area adjacent to Fukushima.
This result suggests that, as in Uchida et al. (2014), it may be more desirable to specify
the area of origin rather than to use the word “domestic,” since the evaluation can besignificantly affected by which area of origin the respondent has in mind.
Based on these results, several policy recommendations can be identified. First, theintroduction of full inspection should be seriously considered. Based on the results from
our analysis, it appears that consumers have very high and robust preference toward
full inspection. That said, the MWTP from stated preference studies like ours is likely
to be an overestimate of the actual value, because respondents are not required to pay
for the product when answer the questions. Therefore, more studies are warranted
before introducing full inspection in a large scale. Second, to raise consumers’ seafood
consumption, it is recommended that scientific and objective information be provided,
rather than emotional and local information. Our results suggest that consumers areunlikely to increase their consumption just because producers are suffering. Also, itappears that there are some regional differences in terms of how information affects
consumers’ evaluation. Thus, it will be more effective if a policy is tailored to each region.
Finally, in addition to providing proper information to consumers, additional policies
may be required to improve the efficiency of market value chains of fishery products. If
additional payment by consumers, intended for helping fishers in disaster areas, aremostly absorbed by other persons in distribution channels as extra revenue, consumer
willingness to pay more may dwindle. The domestic fish distribution channel in Japanis composed of multiple layers of purchasers and middlemen (Yagi et al. (2012)).
Economic inefficiencies in the value chains of fishery products in Japan could also be
addressed as part of a wider restructuring program that includes vertical integrationof production, processing, and distribution sectors.

Notes(1) We thank an anonymous referee for pointing this out.
(2) This profile set was unlikely to be selected for the following reasons: Chilean

salmon is the lowest priced salmon in the market; wild salmon is generally
preferred to farmed salmon in Japan; sample inspection is less preferred to fullinspection; government agencies were losing trust due to its poor information
disclosure; and 400 yen is the highest price tag. This profile set is unlikely to exist- 34 -

Consumers’ Attitude Toward Inspection Methods and Institutions for Potential Radioactive
Contamination: A Choice-based Conjoint Analysis

in a real market and, therefore, we removed this particular profile set from ourchoice experiments to reduce burden of respondents.
(3) Results are similar if we use a limited sample of respondents who is in charge ofgrocery shopping in the household.
(4) We do not consider the option of “no inspection.” As the survey was conducted on
August 2012 when the concern for radioactive contamination was still serious, we
believe that no inspection was not an option.
(5) Note that we cannot compare the magnitude of the parameter estimates acrossthese two columns in this table because these parameter estimates are relative tothe error variance in each sample.
(6) More than one full inspection equipment may be needed to cover the entire

prefecture. Also, we do not find the actual cost estimate for a full sampling
equipment. Even so, however, this additional revenue seems sufficiently large.

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