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Table 5 Logit specifications on WTP responses

From: Impact of environmental and social attitudes, and family concerns on willingness to pay for improved air quality: a contingent valuation application in Mexico City

Explanatory variables

Entire

Excluding highest category

Excluding

Excluding

sample

Income (I)

Age (II)

(I) and (II)

protest responses

Bid

−0.0024***

-0.0024***

−0.0024***

−0.0023***

−0.0019***

(2008 US $)

(0.0003)

(0.0003)

(0.0003)

(0.0003)

(0.0003)

Environmental and social attitudes 

 Air pollution problem is very important (1 if yes; 0 otherwise)

1.1512 (0.2560)***

1.0818 (0.2495)***

1.1728 (0.2575)***

1.0987 (0.2510)***

0.5677 (0.2787)**

 Poverty/economic development problem is very important (1 if yes; 0 otherwise)

−1.1317 (0.4669)*

−1.1207 (0.4657)*

−0.9308 (0.4561)*

−0.9203 (0.4538)*

−1.2010 (0.4642)*

 Both air pollution and poverty problems are very important (1 if yes; 0 otherwise)

1.3957 (0.5054)**

1.4635 (0.5044)**

1.1676 (0.4937)*

1.2383 (0.4921)*

1.4261 (0.5088)***

Family concerns

 Family member sick of respiratory illness or allergy (1 if yes; 0 otherwise)

0.9372 (0.2477)***

0.7538 (0.2462)**

0.8998 (0.2499)***

0.7130 (0.2483)**

0.9495 (0.2695)***

 Car at household (1 if yes; 0 otherwise)

0.4188 (0.2282)

0.5274 (0.2291)*

0.4392 (0.2277)

0.5504 (0.2285)*

0.7003 (0.262)***

 More adults at household than sample median (i.e. 2)

−1.3614 (0.2236)***

−1.1820 (0.2260)***

−1.3782 (0.2240)***

−1.1939 (0.2261)***

−1.6214 (0.2381)***

 More children at household than sample median (i.e. 1)

-0.331 (0.2359)

-0.3832 (0.2327)

−0.2826 (0.2350)

−0.3358 (0.2315)

−0.3456 (0.2596)

Socioeconomic controls

 Male (1 if yes; 0 otherwise)

−0.1644 (0.1956)

−0.0957 (0.1925)

−0.1403 (0.1962)

−0.0703 (0.1932)

−0.7388 (0.2129)***

Job status

 Part-time job

-0.1352 (0.2568)

-0.1198 (0.2508)

-0.1096 (0.2561)

-0.0934 (0.2500)

0.3854 (0.2779)

 Full-time job

1.0362 (0.3469)**

1.0279 (0.3422)**

1.0359 (0.3387)**

1.0267 (0.3335)**

1.6952 (0.3601)***

Range of respondent’s age 

 25–35

0.1011 (0.2473)

0.0565 (0.2427)

0.0948 (0.2465)

0.0479 (0.2418)

−0.7256 (0.3741)*

 35–45

0.1669 (0.3424)

0.1354 (0.3406)

0.1105 (0.3379)

0.0796 (0.3361)

−0.6871 (0.4609)

 45–55

0.9327 (0.4093)*

0.8463 (0.4080)*

0.8960 (0.4098)*

0.8067 (0.4088)*

0.0520 (0.4937)

 >55

3.2530 (0.6821)***

3.2256 (0.6799)***

2.7303 (0.7448)***

Monthly household income (2008 US$)

 US $567–US $967

0.8850 (0.2529)***

0.7802 (0.2463)**

0.8993 (0.2514)***

0.7925 (0.2449)**

1.6086 (0.3336)***

 US $967–US $2167

1.5738 (0.4308)***

1.4101 (0.4227)***

1.5547 (0.422)***

1.3889 (0.4132)***

1.5789 (0.4247)***

 US $2167–US $5000

-2.0399 (0.5151)***

−1.9532 (0.5096)***

−1.9479 (0.5360)***

Respondent’s contribution to monthly household income

 50–75%

1.1867 (0.3164)***

1.2078 (0.3140)***

1.1626 (0.3153)***

1.1854 (0.3133)***

0.8187 (0.3083)**

 >75%

2.9332 (0.8069)***

2.9175 (0.8030)***

2.7959 (0.7570)***

2.7815 (0.7530)***

2.3957 (0.6467)***

Interactions between household income and respondent’s contribution

Income

Contribution

 

US $567–US $967

50–75%

−1.5199 (0.5830)**

−1.4693 (0.5669)**

−1.1988 (0.6195)

−1.1557 (0.6016)

−2.0715 (0.6044)***

Interactions between household income and respondent’s contribution

Income

Contribution

 

US $567–US $967

>75%

−1.783 (1.0377)

−1.7074 (1.0304)

–1.7075 (1.0030)

−1.6251 (0.9954)

−1.8820 (0.9415)*

US $967–US $2167

50–75%

−2.7109 (0.5566)***

−2.6308 (0.5483)***

−2.7178 (0.5544)***

−2.6349 (0.5453)***

−2.2579 (0.5569)

US $967–US $2167

>75%

−2.3054 (1.1840)

−2.2085 (1.1680)

−2.1273 (1.1453)

−2.0363 (1.1294)

-1.7597*

(1.1023)

 Intercept

0.9889 (0.3649)**

0.9174 (0.3568)*

0.9130 (0.3576)*

0.8441 (0.3500)*

1.7013***

(0.4430)

 n

1541

1490

1243

1192

1499

 Pseudo-R2

0.3527

0.3487

0.2989

0.2925

0.3582

 Log-likelihood

−434.7521

−421.9019

−428.6136

−415.6528

-379.1291

  1. Standard errors in parenthesis. Coefficients are significant at *** 99%, ** 95%, or * 90% level of confidence
  2. aReference category: no job
  3. bReference category: 18-25
  4. cReference category: <US$ 567
  5. dReference category: <50%
  6. eNot all interactions are included because of missing cells in the corresponding excluded interaction