The value of natural capital and its determinants in Japan○Junya Kumagai *・Mihoko Wakamatsu*・Shunsuke Managi*○熊谷惇也・若松美保子・馬奈木俊介
1. Introduction
Recently in Japan, natural capital has been gaining attention to researchers and policy makers to realize
sustainability (Kumagai and Managi, 2018). Previous studies have investigated the value of various types ofecosystems that construct natural capital by meta-analysis (Costanza et al., 2014). Other studies have investigatedthe value of specific areas or species. Although these studies have provided information on either the global valueof natural capital or the local value of specific items, there is little evidence on the exhaustive values of naturalenvironment in a specific country, which will provide useful information for the national policy makers. We
investigated Japanese individuals’ perceived value of the various types of Japanese-specific natural environment.
2. Methodology
We analyzed the determinants of WTP to maintain the various types of the elements that construct natural capitalusing the original data collected from a Japanese nationwide survey through internet that we conducted in February
2019. We applied to contingent valuation method (CVM) to elicit individuals’ WTP to maintain Japanese naturalcapital. Payment card method was employed. Even after deleting the protest responses from the analytical sample,
approximately 20% of the respondents still showed zero WTP to most of the items.
In recent empirical studies, zero-inflated ordered probit (ZIOP) model has been applied to ordinal dependent
variables (Harris and Zhao, 2007). Some studies have shown the superiority of ZIOP regression to traditional
ordered probit in providing less biased estimates when an ordinal dependent variable exhibits a high fraction ofobservations at zero (Bagozzi et al., 2012). This model assumed two latent dependent variables through the processof estimation. The latent variable model is represented as the following equations:r * = x ' β + ε,y * = z ' γ + u,

0

y =j
J


if r * ≤ 0
if 0 < r *if 0 < r *orandandy * ≤ 0,μ j −1 < y * ≤ μ j ( j = 1, ..., J − 1),
μJ −1 < y * ,(1)
(2)

(3)

where r* is a latent variable representing the propensity for participation in the WTP decision, x is a vector ofdeterminants of the participation with unknown parameters β, y* is a latent variable related to an ordinal variable ytaking on the values {0, 1, 2, …, J}, z is a vector of determinants of y with unknown parameters γ, ε and u arestandard-normally distributed error terms, and μj (j = 1, …, J – 1) are unknown threshold parameters. The unknown
parameters can be estimated by maximum likelihood estimation. As explanatory variables x and z, we includedsociodemographic variables shown in the next section.
* Department of Urban Engineering, School of Engineering, Kyushu University〒819-0395, 744 Motooka, Nishi-ku, Fukuoka. TEL: 092-802-3408. E-mail: jkumagai.6@gmail.com

3. Results
Table 1 shows the results of ZIOP regression. Explanatory variables are as follows: the dummy for female (Female);
respondents’ age (Age); the dummy for university graduate (Graduate); the number of family members (Householdsize); the number of children (Child); the dummy for worker (Worker); yearly income (10,000 yen) per household(Income); the dummy for living in Tokyo 23 wards or designated cities (Urban); the frequency of visiting thetargeted place (Frequency); perceived importance of maintaining the targeted place (Importance). The results showthat male and younger respondents with smaller household size and higher household income are likely to show
higher WTP to maintain the most of the elements of natural capital that we asked the respondents to value. The
frequency of visits and perceived importance are also likely to increase WTP.
Table 1. γ estimates of ZIOP regression.
VARIABLES

Padd y field

Crop field

Orchard

PasturePlantedfo restNaturalfo restFemale
Age
Graduate
Household size
ChildWorkerIncome
Urban
Frequ en cy
Impo rtanceObservations–0.133***–0.00197
0.0467–0.0132
0.00591
0.01460.000448***–0.0152
0.143***
0.174***
4,437–0.148***–0.00280*
0.0338–0.01810.01670.04140.000456***
0.007440.129***
0.106**
4,440–0.146***–0.00422***0.0194–0.0266
0.0216
0.05240.000460***
0.000499
0.142***–0.05704,427–0.115***–0.00242
0.0616–0.0327*
0.03890.06250.000446***–0.01190.188***–0.0349
4,423–0.0961**–0.00341**
0.0618–0.0348*0.0102–0.01430.000418***0.0141
0.0956***
0.05984,440–0.0788**–0.00337**
0.0660*–0.0321*0.01260.002990.000411***–0.00143
0.116***
0.0788**4,452

Coral reef

Man gro ve

Seaweed bed

Tidal flat

Sand beachFishinggroundFemale–0.0659*Age–0.000566
Graduate
0.0686*Household size
–0.0392**Child
0.0574**
Worker
–0.0151
Income0.000407***
Urban–0.0417Frequ en cy
0.160***
Impo rtance
0.0758*Observations
4,423*** p<0.01, ** p<0.05, * p<0.1–0.102***–0.00213
0.0541–0.0439**0.02350.04460.000425***
0.01200.124***
0.143**
4,397–0.114***–0.00390***0.0470–0.0416**0.0106
0.06780.000461***0.0301
0.0931***0.192***
4,397–0.135***–0.00303**
0.0102–0.0370**0.01300.0829*0.000402***0.04380.112***
0.0182
4,402–0.0617–0.000836
0.0847**–0.0503***
0.0621**–0.01700.000427***–0.0318
0.153***
0.309***
4,414–0.144***–0.00241*
0.0528–0.0441**0.01300.05480.000424***–0.0100
0.0841***
0.0940**4,404

Table 1. (continued)
VARIABLES

Seasideprotection
fo rest–0.0800**–0.00375***
0.0290–0.0327*
0.00895–0.00981
0.000450***
0.02340.113***
0.05564,440Natural
en vironment
in Japan–0.108***0.00216*0.0756**–0.02480.02070.02750.000536***–0.0316
4,499

References
Bagozzi, B. E., Hill, D. W., Moore, W. H., & Mukherjee, B. (2012). Modeling Two Types of Zeros in Ordinal Data : The Zero-inflated Ordered
Probit (ZiOP) Model in Conflict Research. In: Paper Presented at the New Faces in Political Methodology Meeting, Penn State, 30 April 2011.
Costanza, R., de Groot, R., Sutton, P., van der Ploeg, S., Anderson, S. J., Kubiszewski, I., Farber, S., & Turner, R. K. (2014). Changes in the global
value of ecosystem services. Global Environmental Change, 26(1), 152–158.
Harris, M. N., & Zhao, X. (2007). A zero-inflated ordered probit model, with an application to modelling tobacco consumption. Journal ofEconometrics, 141(2), 1073–1099.
Kumagai, J., & Managi, S. (2018). The 5th Basic Environment Plan that promotes natural capital. Review of Environmental Economics and Policy
Studies, 11(2), 57–60 (in Japanese).