Introduction

This research addresses the economic valuation of the hill Tezcotzingo better place known as “baños de Netzahualcóyotl”which is located in San Nicolas Tlaminca, Texcoco, State of Mexico, which was established as a protected area with the category state reserve area called "Tetzcotzinco System" by the government from the State of Mexico (^{Gaceta de Gobierno 2001}). Nowadays natural areas are under constat pressure by different activities like agriculture, urban expantion and resource extraction. However, are environmental assets that society wants to keep, as are useful to both inhabitants of rural areas where they are immersed as inhabitants from the city who visit the place (^{Colombo and Hanley, 2008}).

In this place there is an archaeological site that according to research from the National Institute of Anthropology and History (INAH), was the botanical garden from the tlatoani Netzahualcóyotl, in which still are some endemic plant, species that are endangered; there are also remains of what was an aqueduct that was part of the irrigation system of the garden and even it was the one that provided water to the surrounding towns using some structures dating from around 1431 to 1521 after christ. Ixtlilxóchitl (2007). The method used in the studies to assess such assets is the contingent valuation method (CVM).

The archaeological and natural area known as “baños de Netzahualcóyotl” behaves as a public good and common resource of free access so it lacks market and therefore it also lacks of a market price that reflects its true value. The absence of prices and the little habit of considering natural areas as economic assets that provide goods and services to people has complicated the efficient allocation of such resources (^{Diamond and Hausman, 1994}; ^{Patterson, 1998}; ^{Cooper and Crase, 2008}).

This place is an environmental asset that society wants to keep as it is useful to both the inhabitants of rural areas where it is immersed as for city people visiting the area; currently, it presents problems such as reduced vegetation cover, visitors waste pollution, high rate of erosion, poor state of buildings and gardens, deforestation and extraction of forest resources.

In this context it is necessary to know the value that society makes of it, so it is possible to assign an efficient price for the enjoyment of the area and obtain the resources required to contribute to its conservation. With the above, it is intended to give an economic value as a solution to the problem and thus preserve this archaeological, natural and social assets.

By taking care of the área, the culture and history of the región will be preserved and thus the mexiquense identity can be protected, thus it would preserve and prevent the disappearance of ecosystems from the area which is undergoing heavy deforestation; it could also be used workforce from the place and promote an alternative income that would improve the economy of the people from Texcoco.

The area known as “baños de Netzahualcóyotl” by being an archaeological, natural and social asset, retains a historical and cultural value but due to its deterioration it has been losing. Today becomes important as conservation and restoration of archaeological assets resurfaces, and in particular because the government of the State of Mexico declared a historical monument in 2002.

Regarding to the above, this study raises as general objective: to economically assess the natural and archaeological richness of the area known as “baños de Netzahualcóyotl” for people who knows it or visits it as well as for people who they live in that place. And as specific objective it aimed to determine the willingness to pay of people who visit and live near the archaeological and natural area from “baños de Netzahualcóyotl” and identify the most important socio-economic variables that influence the DAP of people.

The hypothesis tested is that tourists who know and visit the botanical garden from the hill Tezcotzingo and visit the “baños de Netzahualcóyotl” value positively this place and are willing to pay for improvement projects to preserve and care for the area and that its DAP is influenced by variables: age, education, certain quota, gender, marital status and income.

Materials and methods

The methodology used to conduct this research makes use of the contingent valuation method that allows to know DAP by creating a hypothetical market asking the visitors on their willingness to pay. A pilot test was formed from 40 surveys conducted in the area of influence from the hill of Texcotzingo in Texcoco, in the months of November and December 2010. Based on this pilot test was made the estimation of the total sample, which was of 120 surveys and was carried out during the months of December and January, the information obtained from these surveys are shown in the results, which were processed by the computer package Nlogit version 5.

The questionnaire used consisted of four sections. The first corresponded to the introduction in which are data to know if visitors know the place, since when they have noticed changes in the place and if they know what activities carried out in the area. The second section located the activity and degree of interest from visitors regarding deterioration of the área, if there is interest to participate in the preservation of the archaeological area and of the “baños de Netzahualcóyotl” and that related to how it would be interested in participating to preserve the area and what services does the área need. In the third section of the questionnaire sets out the proper economic valuation of Tetzcutzingo system as it investigates about DAP, the amount payable from 12 different amounts in pesos (10, 15, 20, 25, 30, 35, 40, 45, 50 and 55), the time spent to arrive to the hill of Texcotzingo from the place of residence, the cost to reach the area and finally the means of transport used. The fourth and final section collected information from the socioeconomic characteristics of respondents (name, age, gender, place of origin of the respondent, education, occupation and monthly income).

Results and discussion

This section makes reference to the results obtained with the variables price to pay, environmental perception, income and gender, since are the variables used in the model ran on the Nlogit software.

Price to pay. The price to pay is made up of two questions, the first being whether people are willing to pay to preserve the anthropological area and the "Nezahualcoyotl baths"; the second how much they are willing to pay from the different prices that were presented on a card.

86% of respondents are willing to make a payment and 14% are not, exposing various reasons (Table 1).

In this regard the differentiation of the 12 payable amounts was made, which were exposed in 12 different questionnaires, and a total of 120 questionnaires were applied, the results obtained are shown below.

With the above, it can be said that people are willing to allocate a portion of their income to recreation and especially to the conservation of the place of study, although this amount is representative, the ideal amount to pay should be 15 and 20 pesos because this are the amounts that showed a higher percentage of willingness to pay.

Environmental perception. Regarding the attitude and degree of interest of tourists, in this part of the survey a situation of loss or deterioration in the area arises. The first question focuses on whether the respondent is concerned about this deterioration. The results show that 99% of respondents are concerned with the deterioration that the place could have while they do not mind the deterioration is at 1%.

Income. The question related to income, was also divided into six categories and then an average of income for statistical purposes and those not answering an average between the highest and lowest income was made (Table 2).

It was found that only 3% did not answer this question, 7% is represented by people who have an income of less than 1 500 pesos a month, 9% is represented by people with a monthly income above 12 thousand pesos, 20% are people with an income from 6 000 to 12 000 thousand pesos a month, 21% are people with a monthly income of 1 500 to 3 000 thousand pesos and finally 40% are people with an income from 3 thousand to 6 thousand pesos a month.

Gender. The question of gender shows that 63% of respondents were female and 37% male.

Statistical model. The main objective of a contingent valuation study is the estimation of willingness to pay (DAP) as an approximation of the compensating variation, this is done through a process of analysis of a logit model. In probability regressions to respond Yes (1) to the question of willingness to pay and No (0), is always the dependent variable and the fee to pay is one of the independent variables. Next analyses the logit regression model which is specified with the following variables: propensity to say yes, hypothetical price to pay, monthly income, environmental perception and gender.

Results

In this part the results from the program Nlogit are shown. The first part refers to descriptive statistics of the variables used in economic valuation (Table 3 and 4).

In the fit test was obtained an indicator from pseudo McFadden or R² of .1470125 which represents a low value, it is worth mentioning that in this type of study is common to obtain those levels, for example ^{Tyrväinen and Vaanaen (1998)} obtained a value of 0.15 and Mitchel and ^{Carson (1993)} stated that the use of regression models does not seek to validate the valuation method, but to find what variables are those that are related with DAP ^{Larqué et al. (2004)}.

The adjusted pseudo R² of McFadden takes into account the unrestricted likelihood functions which is -68.13722 and the restricted -79.88069 as shown:

Substituting in the equation:

Pseudo R²= 1-(68.13722 /79.88069)= 1-0.85298737= 0.14701263

Therefore it is concluded that the model has a good level of adjustment.

Regarding the dependency test there is that within the statistical analysis also seeks to obtain proof of dependency test, for which is used the restricted and unrestricted likelihood which uses the following formula (Table 5).

LR= -(LnLr - LnL)

Substituting values:

LR= -2(-79.88069- (-68.13722))= 23.48694

Dependency test value for the model:

LR= 23.48694

Acceptable value for models of this type.

The value for the Chi-squared test is 0.0001, so it is concluded that this value is significant for this model.

For the evaluation with individual tests the variable that was significant in statistical terms was price to pay with a value of 0.0001, the next most important was education with 0.1372 but is no longer significant in statistical terms at a level of 95% reliability, the same goes for the third and fourth variable of importance that respectively are environmental perception and gender that at 95% reliability remain to be representative in our model, unless the reliability of our model is reduced.

The model has a percentage of prediction 70 833%, which can be taken as appropriate for being an economic model applied to the environment, to obtain DAP only using the most significant variables found in the model, which were price, income, environmental perception and generated an average DAP that was recorded in this work of $ 41 899 obtaining a minimum DAP of $ 29.3518 and a máximum DAP of $ 50.7263 considering a number of 120 surveys.

Conclusions

This study allowed us to know the various problems that exist in the “baños de Netzahualcóyotl” such as pollution, loss of flora and fauna, the nonexistence of a toll to allow access to the site, disorganization, disintegration of different social groups that help the community, etc. Lack of education, income and opportunities makes people to not give importance to the "Nezahualcoyotl baths", therefore many of them believe that the authorities are solely responsible for solving the problems that arise.

From 100% of respondents 86% are willing to pay and 14% are not willing to pay. Of the 12 prices used in the surey the price of 15 pesos obtained 100% of YES in the 12 questionnaires, so it was the highest price accepted; however, this does not mean that this is the price to pay because at this point were not taken into account any explanatory variable, the DAP in the model has an average of 41.8991 pesos, using all the proposed prices. An important issue that was observed in the study is that women value more and are willing to pay for the conservation of the hill Texcotzingo.

Regarding gender from the 120 respondents 63% were women and 37% men, as the survey was conducted randomly men and women received surveys with different prices, yet most women answered YES to the question willingness to pay. Overall 95% of respondents know the place of study and from this percentage 55% are over 10 years of knowing it and have detected more changes over time such as: the discovery of more archaeological remains, the loss of flora and fauna, the place is polluted with garbage by people that visit the site and finally, natural resources are being lost.

In this type of research, is necessary to count with the help from local authorities to facilitate obtaining information. Also on the part of the application of questionnaires, most of the time people are very reluctant or suspicious with strangers who asked questions regarding socio-economic issues or serious problems involving an expense. The reasons why denial of the DAP was obtained, were mostly of nonconformity and mistrust that interviewed has about the government's capacity and institutions to solve the problem.