IDEAS home Printed from https://ideas.repec.org/a/kap/jproda/v44y2015i1p97-114.html
   My bibliography  Save this article

Consolidating the water industry: an analysis of the potential gains from horizontal integration in a conditional efficiency framework

Author

Listed:
  • Michael Zschille

Abstract

The German potable water supply industry is regarded highly fragmented, thus preventing efficiency improvements that could happen through consolidation. Focusing on a hypothetical restructuring of the industry, we use a cross-section sample of 364 German water utilities in 2006, applying Data Envelopment Analysis, to analyze the potential efficiency gains from hypothetical mergers between water utilities at the county level. A conditional efficiency framework is applied to account for the water utilities’ operating environments. A conditional order-m approach is applied for the detection of potential outlying observations. Merger gains are decomposed into a technical efficiency effect, a harmony effect and a scale effect. The greatest efficiency improvement potentials turn out to result from reducing individual inefficiencies while pure merger gains are found to be low. The results suggest improving incentives for efficient operations in water supply and a consolidation of the smallest water utilities. Copyright Springer Science+Business Media New York 2015

Suggested Citation

  • Michael Zschille, 2015. "Consolidating the water industry: an analysis of the potential gains from horizontal integration in a conditional efficiency framework," Journal of Productivity Analysis, Springer, vol. 44(1), pages 97-114, August.
    • Handle: RePEc:kap:jproda:v:44:y:2015:i:1:p:97-114
    DOI: 10.1007/s11123-014-0407-x
    as

    Download full text from publisher

    File URL: http://hdl.handle.net/10.1007/s11123-014-0407-x
    Download Restriction: Access to full text is restricted to subscribers.
    File URL: https://libkey.io/10.1007/s11123-014-0407-x?utm_source=ideas
    LibKey link: if access is restricted and if your library uses this service, LibKey will redirect you to where you can use your library subscription to access this item
    ---><---

    As the access to this document is restricted, you may want to search for a different version of it.

    References listed on IDEAS

    as
    1. Troels Kristensen & Peter Bogetoft & Kjeld Pedersen, 2010. "Potential gains from hospital mergers in Denmark," Health Care Management Science, Springer, vol. 13(4), pages 334-345, December.
    2. Daraio, Cinzia & Simar, Léopold, 2014. "Directional distances and their robust versions: Computational and testing issues," European Journal of Operational Research, Elsevier, vol. 237(1), pages 358-369.
    3. Cinzia Daraio & Léopold Simar, 2005. "Introducing Environmental Variables in Nonparametric Frontier Models: a Probabilistic Approach," Journal of Productivity Analysis, Springer, vol. 24(1), pages 93-121, September.
    4. Badin, Luiza & Daraio, Cinzia & Simar, Léopold, 2010. "Optimal bandwidth selection for conditional efficiency measures: A data-driven approach," European Journal of Operational Research, Elsevier, vol. 201(2), pages 633-640, March.
    5. Youn Kim, H. & Clark, Robert M., 1988. "Economies of scale and scope in water supply," Regional Science and Urban Economics, Elsevier, vol. 18(4), pages 479-502, November.
    6. Léopold Simar & Paul Wilson, 2011. "Inference by the m out of n bootstrap in nonparametric frontier models," Journal of Productivity Analysis, Springer, vol. 36(1), pages 33-53, August.
    7. Walter, Matthias & Cullmann, Astrid & von Hirschhausen, Christian & Wand, Robert & Zschille, Michael, 2009. "Quo vadis efficiency analysis of water distribution? A comparative literature review," Utilities Policy, Elsevier, vol. 17(3-4), pages 225-232, September.
    8. Cinzia Daraio & Léopold Simar, 2007. "Conditional nonparametric frontier models for convex and nonconvex technologies: a unifying approach," Journal of Productivity Analysis, Springer, vol. 28(1), pages 13-32, October.
    9. Léopold Simar & Paul W. Wilson, 1998. "Sensitivity Analysis of Efficiency Scores: How to Bootstrap in Nonparametric Frontier Models," Management Science, INFORMS, vol. 44(1), pages 49-61, January.
    10. Bottasso, Anna & Conti, Maurizio, 2009. "Scale economies, technology and technical change in the water industry: Evidence from the English water only sector," Regional Science and Urban Economics, Elsevier, vol. 39(2), pages 138-147, March.
    11. Michael Zschille & Matthias Walter, 2012. "The performance of German water utilities: a (semi)-parametric analysis," Applied Economics, Taylor & Francis Journals, vol. 44(29), pages 3749-3764, October.
    12. Garcia, Serge & Moreaux, Michel & Reynaud, Arnaud, 2007. "Measuring economies of vertical integration in network industries: An application to the water sector," International Journal of Industrial Organization, Elsevier, vol. 25(4), pages 791-820, August.
    13. Thanassoulis, Emmanuel, 2000. "The use of data envelopment analysis in the regulation of UK water utilities: Water distribution," European Journal of Operational Research, Elsevier, vol. 126(2), pages 436-453, October.
    14. Marques, Rui Cunha & De Witte, Kristof, 2011. "Is big better? On scale and scope economies in the Portuguese water sector," Economic Modelling, Elsevier, vol. 28(3), pages 1009-1016, May.
    15. Rita Martins & Fernando Coelho & Adelino Fortunato, 2012. "Water losses and hydrographical regions influence on the cost structure of the Portuguese water industry," Journal of Productivity Analysis, Springer, vol. 38(1), pages 81-94, August.
    16. Cazals, Catherine & Florens, Jean-Pierre & Simar, Leopold, 2002. "Nonparametric frontier estimation: a robust approach," Journal of Econometrics, Elsevier, vol. 106(1), pages 1-25, January.
    17. Takuya Urakami & David Parker, 2011. "The Effects of Consolidation amongst Japanese Water Utilities," Urban Studies, Urban Studies Journal Limited, vol. 48(13), pages 2805-2825, October.
    18. Takuya Urakami, 2005. "Identifying scale economies for different types of water supply organizations in Japan," ERSA conference papers ersa05p370, European Regional Science Association.
    19. David Saal & David Parker & Tom Weyman-Jones, 2007. "Determining the contribution of technical change, efficiency change and scale change to productivity growth in the privatized English and Welsh water and sewerage industry: 1985–2000," Journal of Productivity Analysis, Springer, vol. 28(1), pages 127-139, October.
    20. Simar, Leopold & Wilson, Paul W., 2007. "Estimation and inference in two-stage, semi-parametric models of production processes," Journal of Econometrics, Elsevier, vol. 136(1), pages 31-64, January.
    21. Maria Corton, 2011. "Sector fragmentation and aggregation of service provision in the water industry," Journal of Productivity Analysis, Springer, vol. 35(2), pages 159-169, April.
    22. Kristof Witte & Rui Marques, 2011. "Big and beautiful? On non-parametrically measuring scale economies in non-convex technologies," Journal of Productivity Analysis, Springer, vol. 35(3), pages 213-226, June.
    23. Mehdi Farsi & Aurelio Fetz & Massimo Filippini, 2008. "Economies of Scale and Scope in Multi-Utilities," The Energy Journal, International Association for Energy Economics, vol. 0(Number 4), pages 123-144.
    24. Viton, Philip A., 1992. "Consolidations of scale and scope in urban transit," Regional Science and Urban Economics, Elsevier, vol. 22(1), pages 25-49, March.
    25. Bădin, Luiza & Daraio, Cinzia & Simar, Léopold, 2012. "How to measure the impact of environmental factors in a nonparametric production model," European Journal of Operational Research, Elsevier, vol. 223(3), pages 818-833.
    26. Fumitoshi Mizutani & Takuya Urakami, 2001. "articles: Identifying network density and scale economies for Japanese water supply organizations," Papers in Regional Science, Springer;Regional Science Association International, vol. 80(2), pages 211-230.
    27. Fried, Harold O. & Lovell, C. A. Knox & Schmidt, Shelton S. (ed.), 2008. "The Measurement of Productive Efficiency and Productivity Growth," OUP Catalogue, Oxford University Press, number 9780195183528.
    28. Saal David S. & Arocena Pablo & Maziotis Alexandros & Triebs Thomas, 2013. "Scale and Scope Economies and the Efficient Vertical and Horizontal Configuration of the Water Industry: A Survey of the Literature," Review of Network Economics, De Gruyter, vol. 12(1), pages 93-129, March.
    29. Christian von Hirschhausen & Astrid Cullmann & Matthias Walter & Michael Zschille, 2009. "Fallende Preise in der Wasserwirtschaft: Hessen auf dem Vormarsch," DIW Wochenbericht, DIW Berlin, German Institute for Economic Research, vol. 76(10), pages 150-155.
    30. Piacenza, Massimiliano & Vannoni, Davide, 2004. "Choosing among alternative cost function specifications: an application to Italian multi-utilities," Economics Letters, Elsevier, vol. 82(3), pages 415-422, March.
    31. Massimo Filippini & Nevenka Hrovatin & Jelena Zorić, 2008. "Cost efficiency of Slovenian water distribution utilities: an application of stochastic frontier methods," Journal of Productivity Analysis, Springer, vol. 29(2), pages 169-182, April.
    32. Peter Bogetoft & Dexiang Wang, 2005. "Estimating the Potential Gains from Mergers," Journal of Productivity Analysis, Springer, vol. 23(2), pages 145-171, May.
    33. Léopold Simar, 2003. "Detecting Outliers in Frontier Models: A Simple Approach," Journal of Productivity Analysis, Springer, vol. 20(3), pages 391-424, November.
    34. Racine, Jeff, 1997. "Consistent Significance Testing for Nonparametric Regression," Journal of Business & Economic Statistics, American Statistical Association, vol. 15(3), pages 369-378, July.
    35. John K. Ashton, 2003. "Capital Utilisation and Scale in the English and Welsh Water Industry," The Service Industries Journal, Taylor & Francis Journals, vol. 23(5), pages 137-149, November.
    36. Paola Fabbri & Giovanni Fraquelli, 2000. "Costs and Structure of Technology in the Italian Water Industry," Empirica, Springer;Austrian Institute for Economic Research;Austrian Economic Association, vol. 27(1), pages 65-82, March.
    37. Antonioli, B. & Filippini, M., 2001. "The use of a variable cost function in the regulation of the Italian water industry," Utilities Policy, Elsevier, vol. 10(3-4), pages 181-187.
    38. Andres Picazo-Tadeo & Francisco Saez-Fernandez & Francisco Gonzalez-Gomez, 2009. "The role of environmental factors in water utilities' technical efficiency. Empirical evidence from Spanish companies," Applied Economics, Taylor & Francis Journals, vol. 41(5), pages 615-628.
    39. Abbott, Malcolm & Cohen, Bruce, 2009. "Productivity and efficiency in the water industry," Utilities Policy, Elsevier, vol. 17(3-4), pages 233-244, September.
    40. Serge Garcia & Alban Thomas, 2001. "The Structure of Municipal Water Supply Costs: Application to a Panel of French Local Communities," Journal of Productivity Analysis, Springer, vol. 16(1), pages 5-29, July.
    41. Hayfield, Tristen & Racine, Jeffrey S., 2008. "Nonparametric Econometrics: The np Package," Journal of Statistical Software, Foundation for Open Access Statistics, vol. 27(i05).
    42. Giovanni Fraquelli & Massimiliano Piacenza & Davide Vannoni, 2004. "Scope and scale economies in multi-utilities: evidence from gas, water and electricity combinations," Applied Economics, Taylor & Francis Journals, vol. 36(18), pages 2045-2057.
    43. Necmiddin Bagdadioglu & Catherine Waddams Price & Thomas Weyman-Jones, 2007. "Measuring Potential Gains from Mergers among Electricity Distribution Companies in Turkey using a Non-Parametric Model," The Energy Journal, International Association for Energy Economics, vol. 0(Number 2), pages 83-110.
    44. Tupper, Henrique Cesar & Resende, Marcelo, 2004. "Efficiency and regulatory issues in the Brazilian water and sewage sector: an empirical study," Utilities Policy, Elsevier, vol. 12(1), pages 29-40, March.
    45. K De Witte & E Dijkgraaf, 2010. "Mean and bold? On separating merger economies from structural efficiency gains in the drinking water sector," Journal of the Operational Research Society, Palgrave Macmillan;The OR Society, vol. 61(2), pages 222-234, February.
    46. Torres, Marcelo & Morrison Paul, Catherine J., 2006. "Driving forces for consolidation or fragmentation of the US water utility industry: A cost function approach with endogenous output," Journal of Urban Economics, Elsevier, vol. 59(1), pages 104-120, January.
    47. Celine Nauges & Caroline van den Berg, 2010. "Heterogeneity in the Cost Structure of Water and Sanitation Services: A Cross-country Comparison of Conditions for Scale Economies," Oxford Development Studies, Taylor & Francis Journals, vol. 38(2), pages 199-217.
    48. Tim Coelli & Denis Lawrence (ed.), 2006. "Performance Measurement and Regulation of Network Utilities," Books, Edward Elgar Publishing, number 3801.
    49. Peter Bogetoft & Lars Otto, 2011. "Benchmarking with DEA, SFA, and R," International Series in Operations Research and Management Science, Springer, number 978-1-4419-7961-2, September.
    Full references (including those not matched with items on IDEAS)

    Citations

    Citations are extracted by the CitEc Project, subscribe to its RSS feed for this item.
    as


    Cited by:

    1. Agrell, Per J. & Teusch, Jonas, 2020. "Predictability and strategic behavior under frontier regulation," Energy Policy, Elsevier, vol. 137(C).
    2. Contreras, I. & Lozano, S., 2022. "Size efficiency, splits and merger gains, and centralized resource reallocation of Spanish public universities," Socio-Economic Planning Sciences, Elsevier, vol. 81(C).
    3. Arocena, Pablo & Saal, David S. & Urakami, Takuya & Zschille, Michael, 2020. "Measuring and decomposing productivity change in the presence of mergers," European Journal of Operational Research, Elsevier, vol. 282(1), pages 319-333.
    4. Bădin, Luiza & Daraio, Cinzia & Simar, Léopold, 2019. "A bootstrap approach for bandwidth selection in estimating conditional efficiency measures," European Journal of Operational Research, Elsevier, vol. 277(2), pages 784-797.
    5. Devicienti, Francesco & Manello, Alessandro & Vannoni, Davide, 2017. "Technical efficiency, unions and decentralized labor contracts," European Journal of Operational Research, Elsevier, vol. 260(3), pages 1129-1141.
    6. Jianhui Xie & Xiaoxuan Zhu & Liang Liang, 2020. "A multiplicative method for estimating the potential gains from two-stage production system mergers," Annals of Operations Research, Springer, vol. 288(1), pages 475-493, May.
    7. Sebastián Lozano & Belarmino Adenso-Díaz, 2021. "A DEA approach for merging dairy farms," Agricultural Economics, Czech Academy of Agricultural Sciences, vol. 67(6), pages 209-219.
    8. Ying Li & Yung-Ho Chiu & Tai-Yu Lin & Tzu-Han Chang, 2020. "Pre-Evaluating the Technical Efficiency Gains from Potential Mergers and Acquisitions in the IC Design Industry," International Journal of Information Technology & Decision Making (IJITDM), World Scientific Publishing Co. Pte. Ltd., vol. 19(02), pages 525-559, April.
    9. Cinzia Daraio & Léopold Simar & Paul W. Wilson, 2020. "Fast and efficient computation of directional distance estimators," Annals of Operations Research, Springer, vol. 288(2), pages 805-835, May.
    10. Caroline Stiel, 2017. "Modern Public Enterprises: Organisational Innovation and Productivity," Discussion Papers of DIW Berlin 1713, DIW Berlin, German Institute for Economic Research.
    11. Hellwig, Michael & Polk, Andreas, 2021. "Do political links influence water prices? Determinants of water prices in Germany," Utilities Policy, Elsevier, vol. 70(C).
    12. Nickolaos G. Tzeremes, 2019. "Technological change, technological catch-up and export orientation: evidence from Latin American Countries," Journal of Productivity Analysis, Springer, vol. 52(1), pages 85-100, December.
    13. Angeliki Flokou & Vassilis Aletras & Dimitris Niakas, 2017. "Decomposition of potential efficiency gains from hospital mergers in Greece," Health Care Management Science, Springer, vol. 20(4), pages 467-484, December.
    14. Chang, Tsung-Sheng & Lin, Ji-Gang & Ouenniche, Jamal, 2023. "DEA-based Nash bargaining approach to merger target selection," European Journal of Operational Research, Elsevier, vol. 305(2), pages 930-945.
    15. Tourinho, Marco & Santos, Paulo Rosa & Pinto, Francisco Taveira & Camanho, Ana S., 2022. "Performance assessment of water services in Brazilian municipalities: An integrated view of efficiency and access," Socio-Economic Planning Sciences, Elsevier, vol. 79(C).
    16. Michael Zschille, 2016. "Cost Structure and Economies of Scale in German Water Supply," Discussion Papers of DIW Berlin 1576, DIW Berlin, German Institute for Economic Research.
    17. Yan He & Yung-ho Chiu & Bin Zhang, 2020. "Prevaluating Technical Efficiency Gains From Potential Mergers and Acquisitions in China’s Coal Industry," SAGE Open, , vol. 10(3), pages 21582440209, July.
    18. Michael L. Polemis & Thanasis Stengos & Nickolaos G. Tzeremes, 2020. "Modeling the effect of competition on US manufacturing sectors’ efficiency: an order-m frontier analysis," Journal of Productivity Analysis, Springer, vol. 54(1), pages 27-41, August.
    19. Graziano Abrate & Clementina Bruno & Fabrizio Erbetta & Giovanni Fraquelli & Anna Giolitti, 2017. "Efficiency in the Consolidation of the Italian Water Sector," Water Resources Management: An International Journal, Published for the European Water Resources Association (EWRA), Springer;European Water Resources Association (EWRA), vol. 31(8), pages 2447-2463, June.
    20. Alexandr Akimov & Paul Simshauser, 2018. "Performance measurement in Australian water utilities: Current state and future directions," Discussion Papers in Finance finance:201802, Griffith University, Department of Accounting, Finance and Economics.

    Most related items

    These are the items that most often cite the same works as this one and are cited by the same works as this one.
    1. Michael Zschille, 2012. "Consolidating the Water Industry: An Analysis of the Potential Gains from Horizontal Integration in a Conditional Efficiency Framework," Discussion Papers of DIW Berlin 1187, DIW Berlin, German Institute for Economic Research.
    2. Zschille, Michael, 2012. "Consolidating the Water Industry: An Analysis of the Potential Gains from Horizontal Integration in a Conditional Efficiency Fr," CEPR Discussion Papers 8737, C.E.P.R. Discussion Papers.
    3. Michael Zschille, 2014. "Nonparametric measures of returns to scale: an application to German water supply," Empirical Economics, Springer, vol. 47(3), pages 1029-1053, November.
    4. Saal David S. & Arocena Pablo & Maziotis Alexandros & Triebs Thomas, 2013. "Scale and Scope Economies and the Efficient Vertical and Horizontal Configuration of the Water Industry: A Survey of the Literature," Review of Network Economics, De Gruyter, vol. 12(1), pages 93-129, March.
    5. Michael Zschille, 2014. "Marktstrukturen in der Trinkwasserversorgung," DIW Roundup: Politik im Fokus 43, DIW Berlin, German Institute for Economic Research.
    6. Andrea Guerrini & Giulia Romano & Bettina Campedelli, 2013. "Economies of Scale, Scope, and Density in the Italian Water Sector: A Two-Stage Data Envelopment Analysis Approach," Water Resources Management: An International Journal, Published for the European Water Resources Association (EWRA), Springer;European Water Resources Association (EWRA), vol. 27(13), pages 4559-4578, October.
    7. Walter, Matthias & Cullmann, Astrid & von Hirschhausen, Christian & Wand, Robert & Zschille, Michael, 2009. "Quo vadis efficiency analysis of water distribution? A comparative literature review," Utilities Policy, Elsevier, vol. 17(3-4), pages 225-232, September.
    8. Carvalho, Pedro & Marques, Rui Cunha & Berg, Sanford, 2012. "A meta-regression analysis of benchmarking studies on water utilities market structure," Utilities Policy, Elsevier, vol. 21(C), pages 40-49.
    9. Michael Zschille, 2016. "Cost Structure and Economies of Scale in German Water Supply," Discussion Papers of DIW Berlin 1576, DIW Berlin, German Institute for Economic Research.
    10. Augusto C. Mercadier & Walter A. Cont & Gustavo Ferro, 2016. "Economies of scale in Peru’s water and sanitation sector," Journal of Productivity Analysis, Springer, vol. 45(2), pages 215-228, April.
    11. Ferro, Gustavo & Lentini, Emilio & Mercadier, Augusto & Romero, Carlos A., 2010. "Retornos a escala en agua y saneamiento: estimaciones para América Latina [Returns to scale in water and sanitation: estimates for Latin Amercia]," MPRA Paper 20324, University Library of Munich, Germany, revised Jan 2010.
    12. Guerrini, Andrea & Romano, Giulia & Leardini, Chiara, 2018. "Economies of scale and density in the Italian water industry: A stochastic frontier approach," Utilities Policy, Elsevier, vol. 52(C), pages 103-111.
    13. Michael Zschille & Matthias Walter, 2012. "The performance of German water utilities: a (semi)-parametric analysis," Applied Economics, Taylor & Francis Journals, vol. 44(29), pages 3749-3764, October.
    14. Abbott, Malcolm & Cohen, Bruce, 2009. "Productivity and efficiency in the water industry," Utilities Policy, Elsevier, vol. 17(3-4), pages 233-244, September.
    15. Klien, Michael & Michaud, David, 2019. "Water utility consolidation: Are economies of scale realized?," Utilities Policy, Elsevier, vol. 61(C).
    16. Anne-Kathrin Faust & Andrea Baranzini, 2014. "The economic performance of Swiss drinking water utilities," Journal of Productivity Analysis, Springer, vol. 41(3), pages 383-397, June.
    17. Picazo-Tadeo, Andrés J. & Sáez-Fernández, Francisco J. & González-Gómez, Francisco, 2008. "Assesing Performance in the Management of the Urban Water Cycle," Efficiency Series Papers 2008/01, University of Oviedo, Department of Economics, Oviedo Efficiency Group (OEG).
    18. Amir Moradi-Motlagh & Ali Emrouznejad, 2022. "The origins and development of statistical approaches in non-parametric frontier models: a survey of the first two decades of scholarly literature (1998–2020)," Annals of Operations Research, Springer, vol. 318(1), pages 713-741, November.
    19. Endre Bjoerndal & Mette Bjoerndal & Astrid Cullmann & Maria Nieswand, 2016. "Finding the Right Yardstick: Regulation under Heterogeneous Environments," Discussion Papers of DIW Berlin 1555, DIW Berlin, German Institute for Economic Research.
    20. Bjørndal, Endre & Bjørndal, Mette & Cullmann, Astrid & Nieswand, Maria, 2018. "Finding the right yardstick: Regulation of electricity networks under heterogeneous environments," European Journal of Operational Research, Elsevier, vol. 265(2), pages 710-722.

    More about this item

    Keywords

    Water supply; Horizontal integration; Data Envelopment Analysis; Conditional efficiency; Nonparametric estimation; C14; L22; L95; Q25;
    All these keywords.

    JEL classification:

    • C14 - Mathematical and Quantitative Methods - - Econometric and Statistical Methods and Methodology: General - - - Semiparametric and Nonparametric Methods: General
    • L22 - Industrial Organization - - Firm Objectives, Organization, and Behavior - - - Firm Organization and Market Structure
    • L95 - Industrial Organization - - Industry Studies: Transportation and Utilities - - - Gas Utilities; Pipelines; Water Utilities
    • Q25 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Renewable Resources and Conservation - - - Water

    Statistics

    Access and download statistics

    Corrections

    All material on this site has been provided by the respective publishers and authors. You can help correct errors and omissions. When requesting a correction, please mention this item's handle: RePEc:kap:jproda:v:44:y:2015:i:1:p:97-114. See general information about how to correct material in RePEc.

    If you have authored this item and are not yet registered with RePEc, we encourage you to do it here. This allows to link your profile to this item. It also allows you to accept potential citations to this item that we are uncertain about.

    If CitEc recognized a bibliographic reference but did not link an item in RePEc to it, you can help with this form .

    If you know of missing items citing this one, you can help us creating those links by adding the relevant references in the same way as above, for each refering item. If you are a registered author of this item, you may also want to check the "citations" tab in your RePEc Author Service profile, as there may be some citations waiting for confirmation.

    For technical questions regarding this item, or to correct its authors, title, abstract, bibliographic or download information, contact: Sonal Shukla or Springer Nature Abstracting and Indexing (email available below). General contact details of provider: http://www.springer.com .

    Please note that corrections may take a couple of weeks to filter through the various RePEc services.

    IDEAS is a RePEc service. RePEc uses bibliographic data supplied by the respective publishers.