Sustainability Trends in Turkish Tourism: A Longitudinal Analysis of Tourist Arrivals, Overnights and Occupancy Rates (2000–2024)

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The title of the paper looks promising, however the paper treats growth indicators (arrivals, overnights, occupancy) as sustainability proxies and labels TOPSIS rankings as “sustainability performance”.

First of all, the literature review is not sufficient to position the study within existing research. It lacks references to comparable empirical studies and does not engage with established frameworks for measuring tourism sustainability for example “the UN Tourism Statistical Framework for Measuring the Sustainability of Tourism (SF-MST)”. You can see: Measuring Sustainability with Unweighted TOPSIS: An Application to Sustainable Tourism in Spain (https://www.mdpi.com/2071-1050/13/9/5283) and Analysis of factors and strategies for the implementation of sustainable tourism in a green economic structure in China (https://www.sciencedirect.com/science/article/abs/pii/S0959652623041690)

There are also many factual errors. For example: “According to UNWTO, the number of tourists reached 1.5 billion in 2019 in Türkiye.” This is incorrect; 1.5 billion refers to global international arrivals in 2019. And this is not the only one.

The manuscript claims “All the data are provided in the main manuscript,” but only normalized values are shown. Table 1: Years jump from 2006 to 2008 (missing 2007). The min-max results also imply 2000 is the minimum for arrivals/overnights (zeros in 2000).

Please give the raw data.

Equations (2)–(10) need typesetting fixes and explicit definitions 

The statistical analysis presented in the paper is rather simplistic for a study submitted to a scientific journal, such as “Sustainability”. The methodology essentially relies on min–max normalization, year-on-year change calculations, and the application of TOPSIS to rank years. While these steps offer a descriptive overview, they do not provide deeper analytical insights.

No advanced time-series methods are employed (e.g., ARIMA) nor are statistical tests performed to assess the significance of observed changes. In addition, the analysis does not explore potential relationships among the indicators (e.g., whether declines in average length of stay are associated with changes in arrivals or occupancy). Seasonal variation and volatility are also overlooked.

The use of TOPSIS appears primarily as a ranking tool but the justification for choosing this method over alternative approaches is not adequately explained. Given the data structure, the method predictably identifies the most recent years with the largest number of arrivals as the “best” performers, which reduces the analytical contribution of the approach.

Author Response

“We would like to thank the reviewers for their valuable suggestions. The necessary revisions have been made and incorporated into the manuscript, which are highlighted in red for clarity.”

• First of all, the literature review is not sufficient to position the study within existing research. It lacks references to comparable empirical studies and does not engage with established frameworks for measuring tourism sustainability for example “the UN Tourism Statistical Framework for Measuring the Sustainability of Tourism (SF-MST)”. You can see: Measuring Sustainability with Unweighted TOPSIS: An Application to Sustainable Tourism in Spain (https://www.mdpi.com/2071-1050/13/9/5283) and Analysis of factors and strategies for the implementation of sustainable tourism in a green economic structure in China (https://www.sciencedirect.com/science/article/abs/pii/S0959652623041690)

Response 1: We would like to thank the reviewers for their valuable contributions. Relevant data from the UN Tourism Statistical Framework for Measuring the Sustainability of Tourism have been taken and added to the introduction section. In addition, the study literature has been enriched by referencing the mentioned studies.

• There are also many factual errors. For example: “According to UNWTO, the number of tourists reached 1.5 billion in 2019 in Türkiye.” This is incorrect; 1.5 billion refers to global international arrivals in 2019. And this is not the only one.

Response 2: We would like to thank the reviewers for their valuable contributions. The entire manuscript has been edited and necessary corrections have been made.

• The manuscript claims “All the data are provided in the main manuscript,” but only normalized values are shown. Table 1: Years jump from 2006 to 2008 (missing 2007). The min-max results also imply 2000 is the minimum for arrivals/overnights (zeros in 2000).

Response 3: We would like to thank the reviewers for their valuable contributions. the year 2000 is the baseline year with the lowest recorded values in the dataset (Arrivals = 14.0 million, Overnights = 39.1 million). As a result, its normalized values are automatically set to 0, while the year 2024 (Arrivals = 83.2 million, Overnights = 216.0 million) is scaled close to 1 as the maximum. Thus, the zeros in 2000 do not indicate missing or erroneous data, but rather reflect its role as the minimum reference point in the normalization process. We have now added a clarification in the revised manuscript to make this explicit.Raw study data are provided as an appendix in the Appendix section.

• Equations (2)–(10) need typesetting fixes and explicit definitions

Response 4: We would like to thank the reviewers for their valuable contributions. Required revisions made and manuscript revised.

• The statistical analysis presented in the paper is rather simplistic for a study submitted to a scientific journal, such as “Sustainability”. The methodology essentially relies on min–max normalization, year-on-year change calculations, and the application of TOPSIS to rank years. While these steps offer a descriptive overview, they do not provide deeper analytical insights.

Response 5: We would like to thank the reviewers for their valuable contributions. We acknowledge the reviewer’s concern that the statistical approach might appear simplistic. Our main objective, however, was to establish a transparent and replicable framework for long-term monitoring of tourism sustainability trends in Türkiye. Min–max normalization, YoY analysis, and TOPSIS were selected for their methodological clarity and comparability with prior studies. To address the reviewer’s point, we have now clarified the rationale for this choice, highlighted the strengths of using TOPSIS in longitudinal tourism analysis, and added a section on potential methodological extensions (e.g., entropy or CRITIC weighting, panel regression models, and sensitivity analyses). This way, we show that while the current design offers a baseline evaluation, future research can expand towards more sophisticated analytical techniques.

• No advanced time-series methods are employed (e.g., ARIMA) nor are statistical tests performed to assess the significance of observed changes. In addition, the analysis does not explore potential relationships among the indicators (e.g., whether declines in average length of stay are associated with changes in arrivals or occupancy). Seasonal variation and volatility are also overlooked.

Response 6: We thank the reviewer for pointing out these important limitations. Indeed, the current study deliberately focused on providing a long-term descriptive evaluation framework rather than an econometric time-series model. Our dataset consists of annual national-level statistics, which restricted the application of advanced seasonal and volatility analyses. We have now explicitly acknowledged these limitations in the Discussion section. Furthermore, we added suggestions for future research directions, such as ARIMA or VAR models for forecasting, regression-based approaches to test causal links between indicators, and the use of monthly or quarterly data to capture seasonal variation and volatility. We believe these additions clarify the scope of the study and position it as a baseline framework that can be extended by future studies. These limitations are added to the methodology and Results and Discusion sections of the study.

• The use of TOPSIS appears primarily as a ranking tool but the justification for choosing this method over alternative approaches is not adequately explained. Given the data structure, the method predictably identifies the most recent years with the largest number of arrivals as the “best” performers, which reduces the analytical contribution of the approach.

Response 7: We agree that TOPSIS, as a multi-criteria decision-making (MCDM) method, primarily functions as a ranking tool and may appear to produce predictable results when applied to data with steadily increasing arrivals. Our justification for using TOPSIS lies in three points: (i) it allows the integration of multiple indicators (arrivals, overnight stays, average length of stay, occupancy) into a composite sustainability performance index rather than focusing on a single variable; (ii) it provides a transparent, replicable, and policy-relevant ranking framework consistent with prior sustainable tourism studies (e.g., Merino-Muñoz et al., 2021; Zhang et al., 2011); and (iii) it facilitates robustness checks through alternative weighting scenarios, thereby reducing subjectivity. We have now clarified this rationale in the Methods section and explicitly acknowledged the limitations of TOPSIS as primarily a descriptive ranking method. To address the reviewer’s concern, we also highlight in the Discussion that future research could employ alternative methods (e.g., DEA, PCA, or econometric modeling) to validate or complement TOPSIS-based rankings.”

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors analyze the data for a total of 25 years from 2000-2024, with a large time span and rich and comprehensive data, which can present more credible results. The research methodology of the thesis is well-designed, the logic of the thesis is clear, and the analysis of the data is objective and comprehensive. The research methodology is innovative, and the research ideas of the thesis can not only provide reference for the decision-making of the relevant government departments in Turkey, but also provide reference value for scholars in other countries. The following suggestions are for reference:

1. literature: it is suggested to increase the discourse related to the number of tourists and sustainable development in Turkey, which is mentioned in the paper but with less content, which can be increased to make it more in line with the positioning and requirements of this journal.
2. In the data analysis part, the authors have stated the reasons for the data results, which are mostly the subjective views of the authors as seen so far, which can be combined with the views of other scholars or official government reports on the subject, to ensure the objectivity of the academic viewpoints and to increase the degree of academic contribution. Such as the analysis of the reasons in Table 1, lines 203-207. The analyses of the reasons for the other results have similar problems, and it is recommended that they be handled synchronously.
3. Conclusions: It is possible to respond appropriately to the views of other scholars, so that readers can be more aware of the theoretical contribution of the paper. The content of providing advice to government policy makers can also be added, which is more conducive to highlighting the value and significance of the thesis.

Author Response

“We would like to thank the reviewers for their valuable suggestions. The necessary revisions have been made and incorporated into the manuscript, which are highlighted in red for clarity.”

• literature: it is suggested to increase the discourse related to the number of tourists and sustainable development in Turkey, which is mentioned in the paper but with less content, which can be increased to make it more in line with the positioning and requirements of this journal.

Response 1: We thank the reviewer for this valuable suggestion. We have now expanded the literature section by strengthening the discussion on how the rapid growth in tourist arrivals in Türkiye relates to sustainable development challenges and opportunities. In particular, we highlight the implications of rising tourist numbers for resource efficiency, environmental carrying capacity, and socio-cultural sustainability, drawing on prior studies (e.g., Tosun, 2001; Yüzbaşıoğlu et al., 2014; Gössling et al., 2012). This addition aligns the paper more closely with the journal’s scope and enhances its contribution to sustainability debates There are also many factual errors. For example: “According to UNWTO, the number of tourists reached 1.5 billion in 2019 in Türkiye.” This is incorrect; 1.5 billion refers to global international arrivals in 2019. And this is not the only one.

• In the data analysis part, the authors have stated the reasons for the data results, which are mostly the subjective views of the authors as seen so far, which can be combined with the views of other scholars or official government reports on the subject, to ensure the objectivity of the academic viewpoints and to increase the degree of academic contribution. Such as the analysis of the reasons in Table 1, lines 203-207. The analyses of the reasons for the other results have similar problems, and it is recommended that they be handled synchronously.

Response 2: We would like to thank the reviewers for their valuable contributions. The entire manuscript has been edited and necessary corrections have been made.

• Conclusions: It is possible to respond appropriately to the views of other scholars, so that readers can be more aware of the theoretical contribution of the paper. The content of providing advice to government policy makers can also be added, which is more conducive to highlighting the value and significance of the thesis.

Response 3: We thank the reviewer for this valuable suggestion. In the revised version, we have strengthened the Conclusions by explicitly situating our findings in relation to the work of other scholars, thereby clarifying the theoretical contribution of our study. Furthermore, we have added a subsection with concrete policy recommendations for government and tourism policymakers in Türkiye. These additions highlight both the academic value and the practical significance of the study, in line with the scope of Sustainability

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

1. The issues of ensuring sustainable development of the tourism sector in an aggressive post-COVID environment are relevant.

2. This study analyses the long-term performance of Turkish tourism for the period 2000-2024 from a sustainability perspective and provides important implications for the sector. It would be appropriate to show the consistency of the trends considered with global trends in the tourism industry.

3. In order to improve the quality of the article, please describe the purpose, objectives, hypotheses and research methods more clearly and precisely.

4. It would be useful to provide a description of the practical value of the proposed research and its impact on decision-making processes.

5. Please describe in conclusions the prospects for using this study and the factors limiting its application.

 

Author Response

“We would like to thank the reviewers for their valuable suggestions. The necessary revisions have been made and incorporated into the manuscript, which are highlighted in red for clarity.”

• This study analyses the long-term performance of Turkish tourism for the period 2000-2024 from a sustainability perspective and provides important implications for the sector. It would be appropriate to show the consistency of the trends considered with global trends in the tourism industry.

Response 1: We thank the reviewer for this valuable suggestion. We have now expanded the literature section by strengthening the discussion on how the rapid growth in tourist arrivals in Türkiye relates to sustainable development challenges and opportunities. In particular, we highlight the implications of rising tourist numbers for resource efficiency, environmental carrying capacity, and socio-cultural sustainability, drawing on prior studies (e.g., Tosun, 2001; Yüzbaşıoğlu et al., 2014; Gössling et al., 2012). This addition aligns the paper more closely with the journal’s scope and enhances its contribution to sustainability debates There are also many factual errors. For example: “According to UNWTO, the number of tourists reached 1.5 billion in 2019 in Türkiye.” This is incorrect; 1.5 billion refers to global international arrivals in 2019. And this is not the only one.

• In the data analysis part, the authors have stated the reasons for the data results, which are mostly the subjective views of the authors as seen so far, which can be combined with the views of other scholars or official government reports on the subject, to ensure the objectivity of the academic viewpoints and to increase the degree of academic contribution. Such as the analysis of the reasons in Table 1, lines 203-207. The analyses of the reasons for the other results have similar problems, and it is recommended that they be handled synchronously.

Response 2: We would like to thank the reviewers for their valuable contributions. In the revised version, we have expanded the Results and Discussion section by situating the Turkish case within the broader context of global tourism trends. Specifically, we now highlight that international arrivals worldwide reached 1.4 billion in 2024, recovering to 99% of 2019 levels, with an 11% annual growth (UNWTO, 2024). We also note that the global tourism sector contributed a record 11.1 trillion USD to world GDP in 2024 (WTTC, 2024), while long-term projections estimate an average growth rate of 3.3% annually towards 2030 (UNWTO, 2011). Furthermore, the decline in the average length of stay observed in Türkiye is consistent with international patterns, particularly in Europe, where low-cost airlines and changing travel behaviors have encouraged more frequent but shorter trips). These additions demonstrate that the Turkish experience not only reflects domestic dynamics but also aligns with structural transformations in global tourism demand.

 

• To improve the quality of the article, please describe the purpose, objectives, hypotheses, and research methods more clearly and precisely.

Response 3: We thank the reviewer for this valuable suggestion. In the revised version, we have clarified the purpose, objectives, hypotheses, and methods in the Introduction and Materials and Methods sections. Specifically, we now state the overall purpose of the study, outline three specific objectives, formulate the underlying hypotheses regarding tourism sustainability performance in Türkiye, and provide a more precise explanation of the data sources, normalization procedure, YoY analysis, and the rationale for applying the TOPSIS method. These additions improve the transparency and scientific rigor of the paper.

 

• It would be useful to provide a description of the practical value of the proposed research and its impact on decision-making processes.

Response 4: We appreciate this valuable suggestion. In the revised version, we have added a description of the practical implications of the study. Specifically, we highlight how the proposed sustainability performance framework can support policymakers in Türkiye by providing an evidence-based decision-support tool. The ranking of years based on sustainability indicators enables the identification of both high-performing and crisis years, offering insights for policy design, crisis management, and resource allocation. Furthermore, the results can help tourism authorities to develop strategies to extend the average length of stay, diversify tourism products, and reduce occupancy volatility. These additions emphasize the applied value of the research in shaping sustainable tourism policies.

• Please describe in conclusions the prospects for using this study and the factors limiting its application.

Response 5: We thank the reviewer for this important suggestion. In the revised version, we have expanded the Conclusions to explicitly discuss both the practical prospects of using the study and its limitations. Specifically, we highlight how the proposed framework can serve policymakers as a decision-support tool for monitoring sustainability and designing long-term tourism strategies. At the same time, we acknowledge limitations such as the reliance on annual national-level data, the absence of seasonality analysis, and the descriptive nature of the statistical methods. We also indicate directions for future research to address these limitations, including the use of higher-frequency datasets, advanced time-series and econometric techniques, and broader sustainability indicators.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The recommendations were taken into account.

Author Response

We would like to thank the reviewers for their valuable suggestions