{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,5]],"date-time":"2026-08-05T05:45:07Z","timestamp":1785908707398,"version":"3.56.0"},"reference-count":78,"publisher":"Cambridge University Press (CUP)","license":[{"start":{"date-parts":[[2026,8,5]],"date-time":"2026-08-05T00:00:00Z","timestamp":1785888000000},"content-version":"unspecified","delay-in-days":216,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["cambridge.org"],"crossmark-restriction":true},"short-container-title":["Prim Health Care Res Dev"],"published-print":{"date-parts":[[2026]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>This study investigates long-term trends in infant mortality rates (IMRs) in the case of 15 post-Soviet countries, with the aim of testing the Matthew Effect hypothesis, which suggests that inequality in health outcomes tend to persist or even widen over time. To assess these trends comprehensively, we employed various unit root tests, including traditional augmented Dickey\u2013Fuller (ADF), non-linear (KSS, Kruse, Sollis, and Hepsag), and Fourier-based approaches (Fourier KPSS, Fourier ADF, flexible Fourier ADF, flexible fractional Fourier ADF, Fourier KSS, Fourier Kruse, and Fourier Sollis) to the data period from 1982 to 2022. Additionally, the multi-criteria decision analysis (MCDA) methods, such as equal weighting, entropy weighting, and TOPSIS, were utilized for a robustness check. The findings demonstrated that stationarity is validated in Armenia, Azerbaijan, Georgia, Kazakhstan, Kyrgyzstan, Lithuania, Latvia, Tajikistan, Turkmenistan, Ukraine, and Uzbekistan, thereby corroborating the Matthew Effect. Conversely, Belarus, Estonia, Moldova, and Russia exhibit non-stationary IMR series, indicating continued fluctuations or structural changes in their infant mortality patterns. The findings indicate that infant mortality has plateaued in several countries, pointing to stagnation in policy effectiveness. Conversely, some countries show dynamic change, possibly indicating responsive health systems. These insights provide important direction for country-specific health policy design to reduce IMR and health inequality more effectively.<\/jats:p>","DOI":"10.1017\/s1463423626101534","type":"journal-article","created":{"date-parts":[[2026,8,5]],"date-time":"2026-08-05T04:49:02Z","timestamp":1785905342000},"update-policy":"https:\/\/doi.org\/10.1017\/policypage","source":"Crossref","is-referenced-by-count":0,"title":["Investigating the persistence of infant mortality and the Matthew effect in post-Soviet countries: evidence from nonlinear and Fourier-based time-series methods"],"prefix":"10.1017","volume":"27","author":[{"given":"Nijat","family":"Gasim","sequence":"first","affiliation":[{"name":"Qaraba\u011f University"},{"name":"Baku State University"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6248-6120","authenticated-orcid":false,"given":"Shahriyar","family":"Mukhtarov","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05wawjf63","id-type":"ROR","asserted-by":"publisher"}],"name":"Baku Engineering University"},{"name":"Korea University"},{"name":"Vistula University"},{"name":"Azerbaijan University of Architecture and Construction"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8724-8444","authenticated-orcid":false,"given":"Ayse Nur","family":"Sahinler","sequence":"additional","affiliation":[{"name":"Ankara Yildirim Beyazit University"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Aytakin","family":"Afandiyeva","sequence":"additional","affiliation":[{"name":"Azerbaijan University of Architecture and Construction"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Narmin","family":"Alakbarova","sequence":"additional","affiliation":[{"name":"Baku Higher Oil School"},{"name":"Azerbaijan State University of Economics (UNEC)"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"56","published-online":{"date-parts":[[2026,8,5]]},"reference":[{"key":"S1463423626101534_ref42","doi-asserted-by":"publisher","DOI":"10.1162\/003465303772815961"},{"key":"S1463423626101534_ref47","doi-asserted-by":"publisher","DOI":"10.1126\/science.159.3810.56"},{"key":"S1463423626101534_ref57","doi-asserted-by":"publisher","DOI":"10.4054\/DemRes.2021.45.24"},{"key":"S1463423626101534_ref60","doi-asserted-by":"publisher","DOI":"10.1016\/j.heliyon.2024.e29550"},{"key":"S1463423626101534_ref2","doi-asserted-by":"publisher","DOI":"10.1186\/s12889-024-21073-9"},{"key":"S1463423626101534_ref30","doi-asserted-by":"publisher","DOI":"10.1080\/02664760120098739"},{"key":"S1463423626101534_ref68","unstructured":"United Nations Inter-agency Group for Child Mortality Estimation (UN IGME) (2025) Levels & Trends in Child Mortality: Report 2024, New York: UNICEF. Available at https:\/\/data.unicef.org\/resources\/levels-and-trends-in-child-mortality-2024\/ (accessed 20 August 2025)."},{"key":"S1463423626101534_ref50","doi-asserted-by":"publisher","DOI":"10.18517\/ijods.4.2.107-115.2023"},{"key":"S1463423626101534_ref33","volume-title":"Ekonometrik zaman serileri analizlerinde g\u00fcncel y\u00f6ntemler (WinRats Uygulamal\u0131)","author":"Hepsa\u011f","year":"2022"},{"key":"S1463423626101534_ref25","doi-asserted-by":"publisher","DOI":"10.1016\/j.jempfin.2003.03.001"},{"key":"S1463423626101534_ref7","unstructured":"Bishai, D and Poon, A (2001) Does the Law of Diminishing Returns Apply to Infant Mortality Decline? JScholarship Librrary. Available at https:\/\/jscholarship.library.jhu.edu\/server\/api\/core\/bitstreams\/1fc6b7f4-040c-4579-a119-e4a14f16c01d\/content"},{"key":"S1463423626101534_ref65","doi-asserted-by":"publisher","DOI":"10.1038\/s41372-020-00906-6"},{"key":"S1463423626101534_ref10","first-page":"427","article-title":"Distribution of the estimators for autoregressive time series with a unit root","volume":"74","author":"Dickey","year":"1979","journal-title":"Journal of the American Statistical Association"},{"key":"S1463423626101534_ref66","first-page":"270","article-title":"Child mortality in a developing country: A statistical analysis","volume":"4","author":"Uddin","year":"2009","journal-title":"Journal of Applied Quantitative Methods"},{"key":"S1463423626101534_ref77","doi-asserted-by":"publisher","DOI":"10.1093\/pan\/mpr025"},{"key":"S1463423626101534_ref31","first-page":"1","article-title":"A powerful test for linearity when the order of integration is unknown","volume":"12","author":"Harvey","year":"2008","journal-title":"Studies in Nonlinear Dynamics and Econometrics"},{"key":"S1463423626101534_ref56","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0140796"},{"key":"S1463423626101534_ref23","doi-asserted-by":"publisher","DOI":"10.1007\/s13524-017-0553-7"},{"key":"S1463423626101534_ref35","doi-asserted-by":"publisher","DOI":"10.1080\/00324728.1984.10410286"},{"key":"S1463423626101534_ref49","first-page":"15","article-title":"Socio-economic determinants of infant mortality rate in Nigeria: Evidence from autoregressive distributed lag technique","volume":"10","author":"Odjesa","year":"2021","journal-title":"African Journal of Health Economics"},{"key":"S1463423626101534_ref37","doi-asserted-by":"publisher","DOI":"10.1136\/bmj.298.6686.1497"},{"key":"S1463423626101534_ref44","unstructured":"MacMahon, B , Kovar, MG and Feldman, JJ (1972) Infant mortality rates; socioeconomic factors, United States."},{"key":"S1463423626101534_ref6","doi-asserted-by":"publisher","DOI":"10.1186\/1478-7954-7-13"},{"key":"S1463423626101534_ref62","unstructured":"Silva, S (2007) A panel stationarity test for series with breaks in either level or trend. Sydney, NSW: School of Economics and Political Science, University of Sydney."},{"key":"S1463423626101534_ref48","doi-asserted-by":"publisher","DOI":"10.1016\/j.jdeveco.2018.11.002"},{"key":"S1463423626101534_ref51","doi-asserted-by":"publisher","DOI":"10.1016\/j.econlet.2015.07.010"},{"key":"S1463423626101534_ref19","doi-asserted-by":"publisher","DOI":"10.1016\/j.jhealeco.2005.01.004"},{"key":"S1463423626101534_ref26","doi-asserted-by":"publisher","DOI":"10.4054\/DemRes.2019.41.25"},{"key":"S1463423626101534_ref75","doi-asserted-by":"publisher","DOI":"10.1093\/aje\/kwq386"},{"key":"S1463423626101534_ref39","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0220076"},{"key":"S1463423626101534_ref63","doi-asserted-by":"publisher","DOI":"10.1016\/j.econmod.2008.06.002"},{"key":"S1463423626101534_ref72","first-page":"567","volume-title":"Current Methods and Applications in Econometrics","author":"Y\u0131lanc\u0131","year":"2021"},{"key":"S1463423626101534_ref41","doi-asserted-by":"publisher","DOI":"10.1111\/1467-9892.00078"},{"key":"S1463423626101534_ref12","doi-asserted-by":"publisher","DOI":"10.1016\/S0304-4076(01)00073-2"},{"key":"S1463423626101534_ref53","doi-asserted-by":"publisher","DOI":"10.1111\/1467-6419.00064"},{"key":"S1463423626101534_ref20","doi-asserted-by":"publisher","DOI":"10.1186\/1475-9276-10-34"},{"key":"S1463423626101534_ref11","doi-asserted-by":"publisher","DOI":"10.2307\/1912517"},{"key":"S1463423626101534_ref61","doi-asserted-by":"publisher","DOI":"10.1016\/j.indic.2019.100015"},{"key":"S1463423626101534_ref64","unstructured":"The Child Marriage Data Portal (2025) Available at https:\/\/childmarriagedata.org\/country-profiles\/ (accessed 20 August 2025)."},{"key":"S1463423626101534_ref32","doi-asserted-by":"publisher","DOI":"10.1080\/03610918.2018.1563154"},{"key":"S1463423626101534_ref16","doi-asserted-by":"publisher","DOI":"10.1016\/0167-6296(95)00032-1"},{"key":"S1463423626101534_ref45","volume-title":"Unit Roots, Cointegration, and Structural Change","author":"Maddala","year":"2010"},{"key":"S1463423626101534_ref74","doi-asserted-by":"publisher","DOI":"10.3390\/nu12030722"},{"key":"S1463423626101534_ref69","doi-asserted-by":"publisher","DOI":"10.1186\/s12889-019-7111-8"},{"key":"S1463423626101534_ref76","first-page":"91","article-title":"The great equalizer: health care access and infant mortality in Thailand","volume":"6","author":"Gruber","year":"2014","journal-title":"American Economic Journal: Applied Economics"},{"key":"S1463423626101534_ref54","first-page":"51","article-title":"A new unit root test against asymmetric ESTAR nonlinearity with smooth breaks","volume":"22","author":"Ranjbar","year":"2018","journal-title":"Iranian Economic Review"},{"key":"S1463423626101534_ref40","doi-asserted-by":"publisher","DOI":"10.1007\/s00362-009-0204-1"},{"key":"S1463423626101534_ref71","unstructured":"World Bank (2025) World Development Indicators. Available at https:\/\/databank.worldbank.org\/source\/world-development-indicators (accessed 20 August 2025)."},{"key":"S1463423626101534_ref4","doi-asserted-by":"publisher","DOI":"10.1016\/j.ehb.2006.10.003"},{"key":"S1463423626101534_ref24","doi-asserted-by":"publisher","DOI":"10.1007\/s11205-016-1253-1"},{"key":"S1463423626101534_ref29","doi-asserted-by":"publisher","DOI":"10.1111\/j.1368-423X.2007.00203.x"},{"key":"S1463423626101534_ref55","doi-asserted-by":"publisher","DOI":"10.3390\/en13092255"},{"key":"S1463423626101534_ref8","doi-asserted-by":"publisher","DOI":"10.1080\/02664763.2014.980785"},{"key":"S1463423626101534_ref14","doi-asserted-by":"publisher","DOI":"10.1542\/peds.106.1.e5"},{"key":"S1463423626101534_ref43","first-page":"2483","article-title":"Minimum LM unit root test with one structural break","volume":"33","author":"Lee","year":"2004","journal-title":"Manuscript, Department of Economics, Appalachian State University"},{"key":"S1463423626101534_ref9","doi-asserted-by":"publisher","DOI":"10.1016\/j.jimonfin.2010.02.003"},{"key":"S1463423626101534_ref34","doi-asserted-by":"publisher","DOI":"10.1007\/978-3-642-48318-9_3"},{"key":"S1463423626101534_ref27","doi-asserted-by":"publisher","DOI":"10.1080\/03610918.2018.1473591"},{"key":"S1463423626101534_ref22","doi-asserted-by":"publisher","DOI":"10.1186\/s13690-021-00598-0"},{"key":"S1463423626101534_ref59","doi-asserted-by":"publisher","DOI":"10.1016\/j.socscimed.2013.01.010"},{"key":"S1463423626101534_ref38","doi-asserted-by":"publisher","DOI":"10.1016\/S0304-4076(02)00202-6"},{"key":"S1463423626101534_ref58","doi-asserted-by":"publisher","DOI":"10.1080\/07350015.1989.10509723"},{"key":"S1463423626101534_ref67","unstructured":"UK Data Service (2008) Measuring child and infant mortality. Available at https:\/\/ukdataservice.ac.uk\/case-study\/measuring-child-and-infant-mortality\/#:~:text=Impact,drinking%20water%20and%20basic%20sanitation (accessed 30 March 2026)."},{"key":"S1463423626101534_ref18","doi-asserted-by":"publisher","DOI":"10.1186\/s43054-020-00048-6"},{"key":"S1463423626101534_ref3","doi-asserted-by":"publisher","DOI":"10.1111\/j.1467-9892.2006.00478.x"},{"key":"S1463423626101534_ref70","doi-asserted-by":"publisher","DOI":"10.1186\/s12889-021-10397-5"},{"key":"S1463423626101534_ref13","doi-asserted-by":"publisher","DOI":"10.2139\/ssrn.651985"},{"key":"S1463423626101534_ref52","doi-asserted-by":"publisher","DOI":"10.2307\/1913712"},{"key":"S1463423626101534_ref5","doi-asserted-by":"publisher","DOI":"10.1002\/hec.4730040302"},{"key":"S1463423626101534_ref28","doi-asserted-by":"publisher","DOI":"10.1080\/00220380412331293687"},{"key":"S1463423626101534_ref78","doi-asserted-by":"publisher","DOI":"10.1023\/A:1016275505152"},{"key":"S1463423626101534_ref1","unstructured":"Aguirre, A and Vela-Pe\u00f3n, F (2015) Infant Mortality reduction in Mexico: Is there a Matthew Effect? Statistical, Stochastic and Data Analysis Methods & Applications, 185."},{"key":"S1463423626101534_ref15","doi-asserted-by":"publisher","DOI":"10.1016\/j.econlet.2012.04.081"},{"key":"S1463423626101534_ref36","doi-asserted-by":"publisher","DOI":"10.62433\/josdi.v2i2.34"},{"key":"S1463423626101534_ref73","doi-asserted-by":"publisher","DOI":"10.1080\/07350015.1992.10509904"},{"key":"S1463423626101534_ref17","doi-asserted-by":"publisher","DOI":"10.1016\/j.sbspro.2013.10.467"},{"key":"S1463423626101534_ref21","doi-asserted-by":"publisher","DOI":"10.14254\/2071-8330.2025\/18-1\/10"},{"key":"S1463423626101534_ref46","first-page":"52","article-title":"Examining the dynamics of infant mortality rates: A time series analysis","volume":"2","author":"Mehdi","year":"2019","journal-title":"Journal of Policy Options"}],"container-title":["Primary Health Care Research &amp; Development"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.cambridge.org\/core\/services\/aop-cambridge-core\/content\/view\/S1463423626101534","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,8,5]],"date-time":"2026-08-05T04:49:24Z","timestamp":1785905364000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.cambridge.org\/core\/product\/identifier\/S1463423626101534\/type\/journal_article"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026]]},"references-count":78,"alternative-id":["S1463423626101534"],"URL":"https:\/\/doi.org\/10.1017\/s1463423626101534","relation":{},"ISSN":["1463-4236","1477-1128"],"issn-type":[{"value":"1463-4236","type":"print"},{"value":"1477-1128","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026]]},"assertion":[{"value":"\u00a9 The Author(s), 2026. Published by Cambridge University Press","name":"copyright","label":"Copyright","group":{"name":"copyright_and_licensing","label":"Copyright and Licensing"}},{"value":"This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https:\/\/creativecommons.org\/licenses\/by\/4.0\/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.","name":"license","label":"License","group":{"name":"copyright_and_licensing","label":"Copyright and Licensing"}},{"value":"This content has been made available to all.","name":"free","label":"Free to read"}],"article-number":"e84"}}