Distribution Of Birth Dates Research Articles

Relative age effect in male and female elite international amateur boxing

ABSTRACT This study aimed to determine whether the Relative Age Effect (RAE) was present in different sexes and age categories in 12 elite-level international amateur boxing competitions. A total of 4813 athletes competing between 2013 and 2022 were analysed. Athletes were split into four quartiles according to their birth date and compared to the expected (equal) birth date distribution using chi-squared goodness of fit. The results revealed greater RAE prevalence in youth compared to the senior group. RAE was more prominent in males compared to females, with the female group showing an inverse RAE trend. Odds ratio (OR) showed an overrepresentation of male boxers born in Q1 compared to Q4 (OR > 1.19-1.33), while senior female boxers presented an inverse trend (OR < 0.95). Odds Ratios for medallists within the youth group were greater than 1.07 (except Q3 × Q4 = 0.93) highlighting an overrepresentation of boxers born earlier in the year. A shift in strategy to reduce the RAE in young boxers whereby coaches focus less on the short-term pursuit of sporting success is encouraged. Organisations and coaches should increase awareness and provide systematic education around RAE, whilst creating equal competitive opportunities for all young boxers to reduce the extent of RAE in boxing.

Selection and re-selection throughout a national talent pathway: Exploring longitudinal relative age effects in Northern Ireland male soccer

ABSTRACT The purpose of this study was to investigate the longitudinal prevalence of relative age effects (RAEs) across playing levels and positions in Northern Ireland international male soccer. Birthdates of U17 (n = 276), U19 (n = 320), U21 (n = 331), and senior (n = 108) international players between 2011 and 2023 were recorded. Chi-square tests and odds ratios with 95% confidence intervals were used to compare observed and expected birthdate distributions. A selection bias toward relatively older players was evident at U17 and U19 playing levels as well as defensive and midfield positions. In contrast, more relatively younger senior and forward players were selected. Longitudinal analyses revealed that of those players who were initially selected at U17, more relatively older players were re-selected at subsequent playing levels, but there were no birthdate asymmetries amongst new players added after U17. The results of this study demonstrate RAEs are prevalent across Northern Ireland international male soccer and are influenced by playing level as well as position. These findings have important implications for policy makers and practitioners as relatively older players are overrepresented at youth but not senior level, which questions the efficacy of this (un)conscious bias in the talent pathway.

Anomalous distributions of birthdates across days of the month: An analysis using Spanish statistical records

This study investigates birthdate patterns in a context of well-established civil registers and intensive migration inflows. Leveraging extensive Spanish microdata on residential variation flows and the Spanish Municipality Register, this research reveals new facets of the distributions of immigrants’ birthdates across days of the month that differ significantly from those of non-migrants. The registered days of the month for birthdates are categorized into six distinct types based on the assumption that the anomalous distributions of birthdates will display rounding or simplifying patterns (digit preferences). The investigation reveals important anomalies in the distribution of birthdates that are much more pronounced for immigrants. A notable concentration of recorded birthdates is confirmed within all the designated types, contrasted by an under-recording of births on the remaining days of the month. These anomalies depend primarily on migrants’ country of origin and age group. The paper ends by proposing some recommendations for mitigating the anomalies.

Career trajectories, transition rates, and birthdate distributions: the rocky road from youth to senior level in men's European football.

This study aimed to assess youth-to-senior transition rates, quantify the magnitude of relative age effect (RAEs), and evaluate how RAEs affect these transitions in 9,527 men's national football players of England, France, Germany, Italy, and Spain. Regardless of national team, only -15%, 25%, and 40% of U17, U19, and U21 players successfully transitioned to the senior team, respectively, whilst -14%-24% progressed to senior level without being selected during youth. Data suggested a skewed birthdate distribution favouring relatively older players at U17, U19, and U21 levels across all countries, whereas RAEs were also present in England, Italy, and Spain at senior level. Youth-to-senior transition rates were modulated by birthdate at U17 and U19, whereby Q4 players were -2 and 1.5 times more likely to successfully transition at senior level than Q1 players, respectively. Selection at youth international level does not guarantee selection at senior level, but does make it more likely. Moreover, relatively younger athletes are disadvantaged in youth categories, although are more likely to transition to senior level once they have entered the pathway.

Relative Age Effects and the Premier League’s Elite Player Performance Plan (EPPP): A Comparison of Birthdate Distributions Within and Between Age Groups

Relative Age Effects and the Premier League’s Elite Player Performance Plan (EPPP): A Comparison of Birthdate Distributions Within and Between Age Groups

Testing truncation dependence: The Gumbel–Barnett copula

In studies on lifetimes, occasionally, the population contains statistical units that are born before the data collection has started. Left-truncated are units that deceased before this start. For all other units, the age at the study start often is recorded and we aim at testing whether this second measurement is independent of the genuine measure of interest, the lifetime. Our basic model of dependence is the one-parameter Gumbel–Barnett copula. For simplicity, the marginal distribution of the lifetime is assumed to be Exponential and for the age-at-study-start, namely the distribution of birth dates, we assume a Uniform. Also for simplicity, and to fit our application, we assume that units that die later than our study period, are also truncated. As a result from point process theory, we can approximate the truncated sample by a Poisson process and thereby derive its likelihood. Identification, consistency and asymptotic distribution of the maximum-likelihood estimator are derived. Testing for positive truncation dependence must include the hypothetical independence which coincides with the boundary of the copula’s parameter space. By non-standard theory, the maximum likelihood estimator of the exponential and the copula parameter is distributed as a mixture of a two- and a one-dimensional normal distribution. For the proof, the third parameter, the unobservable sample size, is profiled out. An interesting result is, that it differs to view the data as truncated sample, or, as simple sample from the truncated population, but not by much. The application are 55 thousand double-truncated lifetimes of German businesses that closed down over the period 2014 to 2016. The likelihood has its maximum for the copula parameter at the parameter space boundary so that the p-value of test is 0.5. The life expectancy does not increase relative to the year of foundation. Using a Farlie–Gumbel–Morgenstern copula, which models positive and negative dependence, finds that life expectancy of German enterprises even decreases significantly over time. A simulation under the condition of the application suggests that the tests retain the nominal level and have good power.

The developmental activities of women’s professional pathway cricketers

ABSTRACT The growth of investment in women’s cricket has led to the development of new professional pathways. However, there is lack of specific evidence to support the development of these athletes. This study aimed to take a first step in understanding the participation histories of female cricketers selected into English women’s professional academies. 84 players completed the Participation History Questionnaire (PHQ) to capture details of activities engaged in across development, including milestones, cricket activity, and engagement in other sport activities. There were relative age effects where players' birthdate distributions differed from national norms (X 2 = 8.451, p = .003, V = 0.227), and more players than expected attended independent schools (X 2 = 7.980, p = .005, V = 0.232). Participants engaged in cricket informally before coach led training, have siblings (particularly brothers) interested in cricket and often played boy’s cricket before engaging in the girl’s or women’s game. Developmental activities were characterised by early engagement, high levels of diversification, and very low levels of play compared to high levels of formal practice and match play. These findings have implications for the advancement of talent identification and development policies and processes in women’s cricket.

Relative Age Effect Analysis in the History of the Ballon d'Or (1956-2023).

Ballon d'Or is the most important individual award in football, and is a significant measure of excellence. From our knowledge, this is the first study that explored the relative age effect (RAE) throughout the history of the Ballon d'Or. A total of 1899 football players nominated for the award from the first edition in 1956 to the most recent edition (2023) were analyzed. To assess the RAE, the birthdate distributions were categorized into four trimesters. The comparison involved correcting for the uniform distribution using chi-square analysis, with Cramer's V serving as a measure of effect size. Standardized residuals were computed to identify quarters that exhibited significant deviation from the expected values. Odds Ratio and 95% confidence intervals were used to identify discrepancies between trimesters. The results indicated a pronounced presence of an RAE at the global level. However, the longitudinal analysis revealed variations in the behavior of the RAE over time. In the initial decades, there is an overrepresentation of players born in the last months of the year. Subsequently, there is no discernible RAE. In the most recent decades, there has been a clear resurgence of RAE, with an overrepresentation of players born in the first quarters of the year.

Disentangling Gender and Relative Age Effects in Women's and Girls' Rugby Union.

Relative age effects (RAEs) within sports refer to the overrepresentation of athletes born earlier in the selection year and the underrepresentation of those born later in the selection year. Research examining RAEs in women's and girls' rugby union remains limited in comparison to the male literature, whilst the impacts of RAEs on the youth-senior transition are yet to be explored in a female sport context. As such, the purpose of this study was to examine RAEs during entry into the women's and girls' premiership and international rugby union pathways in England, as well as to compare them to their respective senior cohort (n = 1367): (a) U18 England Rugby Centre of Excellence Player (n = 325) vs. Senior Premiership Player (n = 868), and (b) U18 England Player (n = 49) vs. Senior England Player (n = 125). Chi-square (χ2) analyses compared birth quarter (BQ) distributions against expected distributions. The findings revealed no significant difference in BQ distributions at either youth or senior levels, as well as no significant differences in the BQ distributions of those who were likely to transition from youth to senior levels (all p > 0.05). Importantly, though, descriptive statistics showed a skewed birthdate distribution in both U18 England Rugby Centre of Excellence Player (BQ1 = 30% vs. BQ4 = 20%) and U18 England Player cohorts (BQ1 = 33% vs. BQ4 = 18%). We highlight the gender-specific mechanisms that potentially explain the variations between male and female RAEs in rugby union, including developmental differences, sport popularity, and sociocultural norms. We also warn against a 'copy and paste' template from the male provision to ensure the recent growth of female rugby union does not fall victim to the same RAEs in the future.

The relative age effect and its influence on athletic performance in Chinese junior female' tennis players.

The relative age effect (RAE) has been the focus of numerous studies; however, there are still fewer studies in women's sports than in men's sports. In this study, all female players (N = 2,255) who participated in Chinese junior tennis competitions (U12, U14, U16, and the National Junior Team) from 2014 to 2019 were investigated in terms of competitors' birth dates and year-end rankings. For the purposes of the analysis, the birth dates were also separated into quarters and half years. The study's objectives were to analyze the prevalence of the RAE among young Chinese female tennis players and to further examine how the RAE affects athletic performance. Differences between the observed and expected distributions of birth dates were tested using the chi-square statistic, and subsequent calculations were tested using odds ratios. The RAE was discovered to be present in every group of Chinese junior female tennis players (p < 0.001), with the proportions of those born in the first half of the year being 56.4% (U12), 53.1% (U14), and 57.0% (U16), respectively. The RAE for athletes selected for the National Women's Junior Tennis Team was even more significant, with the percentage of birth dates in the first half of the year at 61.2%. Finally, we observed a tendency for the effect of the RAE on the athletic performance of adolescent female tennis players to diminish with age.

Is There a Relationship Between Birth Quartile and Vertical Jump Performance Among Young Male Elite Volleyball Athletes?

Vertical jump is an important skill that influences volleyball performance. In this study, we analyzed the relationship between vertical jump performance and birth quartile of Brazilian male youth volleyball players. We calculated chi-square goodness-of-fit tests to compare the athletes' birthdate distributions in quarters of their birth years (Q1, Q2, Q3, and Q4) according to player age categories (U17, U18, U19, and U21). We calculated one-way ANOVAs to compare spike jump and block jump heights of players born in different quarters of the same year. Overall, we found a relative age effect (i.e., more players with birth dates early in the birth year) in U17 (p < .001), U18 (p < .001), U19 (p < .001), and U21 (p = .04). Regarding vertical jump performance, U18 athletes born in Q2 reached higher spike jump heights (p = .006) and block jump heights (p = .002) than athletes born in Q4, and U19 athletes born in Q1 reached higher block jump heights than athletes born in Q3 (p = .049). There were no significant differences in vertical jump performance across birth quartiles among U17 and U21 athletes. Thus, a relative age effect was present in all age categories but not always reflected in vertical jump performance. Volleyball coaches and policymakers are still advised to employ strategies to ensure fairer opportunities for players born later in the year of their eligibility dates, as we found RAE to be sometimes, but not always, related to higher spike or block jump heights even among these older adolescents and young adult athletes.

The Relative-Age Effect in Male Japanese Football: A CrossSectional Analysis from Youth to Senior Competitive Level

The objective of this study was to examine the magnitude and persistence of the Relative-Age Effect (RAE) in competitive Japanese youth and senior football. A cross-sectional analysis of birthdate distributions of Japanese male youth academy football players (n= 4,488) from the U12 (n=268), U13 (n=481), U14 (n=464), U15 (n=483), U18 (n=1059) and professional players (n=1733) in the 2022 season was conducted. Chi-square goodness of fit tests and Cramer’s V tests were carried out to reveal the incidence and effect size of the RAE across the age categories. A significant RAE (P&lt; .001) was found. It became more pronounced with age, peaking in the U18 age group (Cramer's V= 0.436; Q1/Q4 OR 6.04) before declining in senior professional players (Cramer's V= 0.204; Q1/Q4 OR=2.23). The organisation of youth competition in Japan, with a transition from annual age groups up to U15 to the U18 age group representing three years (U16, U17, and U18) appears to increase the selection bias towards early born players to the detriment of those born later in the age group. However, the transition to senior football saw, compared with the U18 proportions, a reduced proportion of Q1 players, a very similar proportion of Q2 players and increased proportions of Q3 and particularly Q4. The clear implication is that a Q3 and Q4 youth player represents a better prospect for senior professional football than Q1 or Q2 and Q2 than Q1.

The relative age effect among Chinese junior men's tennis players and its impact on sports performance.

The relative age effect (RAE) has been the subject of many studies, but no relevant literature has discussed the phenomenon of RAE in Chinese tennis. Numerous studies have demonstrated that RAE significantly contributes to brain drain and other occurrences that create inequity. This paper analyzes the birth dates and year-end rankings of all male players (N = 2697) who participated in China's junior tennis tournaments (U12, U14, U16) between 2014 and 2019 and who were selected for China's National Junior Team in 2019 and 2020; the paper classifies the birth dates into quarters and semesters. One of the research objectives of this study is to analyze whether RAE exists in Chinese junior men's tennis and whether RAE exerts an effect on athletes' performance. Differences between the observed and expected birthdate distributions were tested using chi-square statistics, and subsequent calculations were tested using odds ratios. The study found that RAE was present in all Chinese junior male tennis sports groups (p<0.001). The percentages of athletes born in the first half of the year were 56.4% (U12), 60.4% (U14), and 60.4% (U16), and the percentages of those born in the first quarter were 34.1% (U12), 36.4% (U14), and 37.1% (U16). Athletes with birth dates closer to the beginning of the year had a higher probability of achieving excellent athletic performance as a result of RAE, whereas those who were born near the end of the year had a more difficult time achieving strong athletic performance.

Junior to senior transition pathway in Italian Football: The rocky road to the top is not determined by youth national team's selections.

Football is a popular sport, but little is known about the youth-to-senior transition rates in elite players, particularly in large and successful countries. This study aims to investigate the youth-to-senior transition rate in the Italian national football team, both prospectively and retrospectively, and to explore if Relative Age Effects (RAEs) affect this transition. Data from 885 players selected in youth and senior Italian national teams between 2000 and 2021 were included in the study. For each player, the birthdate and the number of selection in Under 16, 17, 19, 21 and senior team was considered. The transition rate was determined by the number of youth players competing in the Senior National team (and vice versa), whilst birth quarter (Q) distributions with a chi-square goodness-of-fit test. Prospectively, the transition rate increased as age increased (i.e., from ~20% in U16 to ~50% in U19). Retrospectively, less than 10-20% of youth players were subsequently selected for the senior team. Data revealed a skewed birth date distribution in all age groups, and the RAEs magnitude decreased when age increased (i.e., ORs for Q1 vs Q4 was ~ 9 in U16 and ~ 1.7 in senior teams). Nevertheless, the RAE magnitude was smaller for successfully transitioned players. In conclusion, most players in the senior team were not previously selected for youth teams suggesting that junior international experience may not be a prerequisite for later success. Moreover, while the birthdate strongly influences the selection of youth national teams, its impact is less evident in the youth-to-senior transition.

The birthplace and relative age effects in Brazilian olympic athletes: a cross-national comparison.

Our purpose was to verify the existence of birthplace and relative age effect (RAE), as well as the association between birthplace effect and RAE among Brazilian athletes competing in the Olympic Games. Data included information about Brazilian Summer Olympic athletes from 1920 to 2021. To investigate RAE, athletes' birthdate was distributed into birth quartiles (Q1: Jan-Mar; Q2: Apr-Jun; Q3: Jul-Sep; Q4: Oct-Dec), while birthplace effect was assessed considering the state and the region (Southeast; Northeast; South; North; and Midwest) of birth. The Chi-square test (χ2) was used to verify differences between the birthplace effect and RAE. The sample consisted of 388 Brazilian athletes of both sexes, distributed in 38 sports modalities from 23 Brazilian states (Southeast = 66.5%; South = 14.4%; Northeast = 12.1%; North = 1.5%; Midwest = 5.4%). For both sexes, most of the athletes were from the São Paulo state (37.4%), followed by Rio de Janeiro (18.3%), both from the Southeast region. For birthdate distribution according to birthplace, it was observed that the North region presented the highest frequency of athletes born in Q1 (50%), followed by the Northeast and Southeast regions. No significant differences were found for the birthplace effect (χ2 = 5.69, value of p = 0.128) and RAE between sexes (χ2 = 0.530, value of p = 0.912), nor was shown an association between the birthplace effect and RAE. Most Brazilian Olympic athletes are from the Southeast region, but no RAE was established regarding their birthplace. Results from the present study can guide sports public policies in Brazilian regions, especially in the Midwest, North, and Northeast regions, which are underrepresented in Brazilian high-performance sports.

Effect of Maturity Status and Relative Age Effect on Anthropometrics and Physical Performance of Soccer Players Aged 12 to 15 Years

Introduction: There is a growing interest in the relationship between biological maturation, relative age effect, and soccer sports performance. Based on their cohort's relative age effect and maturation, relatively older soccer players can be favored to be selected for high-level teams. Therefore, the current study examined the effect of maturity and relative age on anthropometric and physical performance tests. Methods: A cross-sectional study involving 82 boys (M age: 13.4 ± 1.1; M body mass: 51.9 ± 9.9; body height: 162 ± 10.5; body fat%: 9.7 ± 1.1) were assessed for anthropometric, flexibility, hand, and leg strength, and countermovement jump performance. Peak height velocity (PHV) determination was used for maturity status estimation. The birthdate distributions were categorized into four quartiles (January-March, Q1; April-June, Q2; July-September, Q3; October-December, Q4). MANOVA analysis was performed on all anthropometric and physical performance assessments to examine differences within age groups and maturity status groups. Differences among all groups were revealed, with high scores in the older group (U-15). Results: Biological maturation influences the differences in the anthropometric and physical performance assessment with a significant effect on the early matured soccer players compared to the late matured. Early matured players were overrepresented and statistically had better anthropometric and physical performance results. Conclusion: However, there was no significant representation of players in the first quarter compared to the third and fourth quarters for all the anthropometric and performance assessments. The current findings can be used for quantifying and controlling performance data of soccer players adjusted to biological requirements used in the training process.

A comparative examination of World Cup Champions of European and American origin of national football players in terms of "relative age effect"

This study aimed to analysis the birth date distributions of the champion players between the years 1930-2022 to determine whether the FIFA World Cup champion national team football players between the years 1930-2022 were affected by the "Relative Age Effect" phenomenon. The universe of the research consisted of the national teams that were champions in the 1930-2022 FIFA World Cup Finals. The samples consisted of the football player group of the national teams that won the championship. The model of the research was determined as "Basic Qualitative Research". The data collection technique in the research was determined as "Document Analysis". The data analysis was made according to the Miles &amp; Huberman model, which is a descriptive analysis form. In the study, the information of the athletes was detailed by looking at the squad structure for the FIFA World Cup champion national team football players between the years 1930-2022. In the highest level of professional football, it has been seen that the champion national team football players are numerically close to each other in terms of "relative age effect". As a result, it has been observed that the relative age effect in senior football decreases with increasing age. It was shown that the relative age effect in professional elite national teams changed negatively due to the high number of football players born in the second half of the year. In this case, it was not a negative situation for football players who transition to professionalism and reach the elite level, being born in the last months of the year. Looking at the intercontinental comparison, even considering the different football culture and structure, it has been revealed that late-born athletes have caught up with their peers at a professional level and even left them behind.

Relative age effect

The aim of this study was to examine relative age effect (RAE) on distinctive variables and age groups in recreational football. Participants (N = 79,249) included male (n = 63,540) and female (n = 15,709) players aged 2 to 12 years. Data were gathered through an official database containing all licensed players in Denmark. Birthdate distributions were split by age category, sex, club size, year group size, and birth quarter (Q1 = January to March, Q4 = October to December). RAEs were calculated using chi-square analysis. Significant RAEs existed in all age categories (except females in U6 and below). The effect was most pronounced at the entry level among both males and females. Club size was not associated with RAEs, but were shown in smaller and midsized year groups, but were absent in larger year groups. The results of this study show that RAEs are present from early sport participation.

Youth-to-senior transition in women's and girls' football: Towards a better understanding of relative age effects and gender-specific considerations.

This study aimed to evaluate youth-to-senior transition and the relative age effect in Italian female football national teams. Birthdate data of 774 female players selected for Under 17 (N = 416), 19 (N = 265) and National Senior team (N = 93) were analysed. The youth-to-senior transition rate was determined by the number of youth players competing in the Senior National team (and vice versa), whilst birth quarter (Q) distributions with a chi-square goodness-of-fit test. Only 17.4% of youth players were able to be selected for the Senior National team, whereas 31.2% of the players reached the high-senior level without being selected for youth age groups. Data revealed a skewed birth date distribution in Under 17 and 19 teams (on average, Q1 = 35.6% vs Q4 = 18.5%) but not in the Senior National team. Youth players born in Q1 were two times more likely to be selected than in Q4. In Under 17, goalkeepers, defenders, and midfielders of Q1 players were overrepresented. However, Q4 players recorded higher conversion rates than Q1 (Q1 = 16.4% vs. Q4 = 25.0%). National youth experience may not be a prerequisite for being selected at the senior level. Moreover, this confers a higher probability of playing in the National Senior team than players not selected in youth rosters.

Relative Age Effect in Judo Competitions: Influence of Age, Weight Category, Sex, and Time Frames

This study was conducted to determine whether the relative age effect (RAE) is present in different age groups, weight categories, sexes, and across different time frames in international-level judo competition. A total of 9451 judo athletes competing at the Olympic Games and/or World Championships in the Cadet, Junior and/or Senior age groups between 1993 and 2020 were considered. Athletes' birthdate distributions were grouped in four quartiles (Q1: January-March; Q2: April-June; Q3: July-September; Q4: October-December) and compared to a day-corrected theoretical distribution using Chi-squared analysis. Poisson regression was also used to evaluate the ability to explain weekly birth count. RAE was more prevalent in males than females (p < .05), and for Cadets and Juniors compared to Seniors (p < .05). Heavyweight and middleweight categories presented RAEs in Senior and Junior males, while for females it was present in Cadet heavyweights (p < .05). RAE was more prevalent in recent years (2009-2021) for Senior male judo athletes (p < .05). Poisson analysis illustrated some nuanced information, including RAE detection during an earlier time frame, not readily apparent with the traditional analysis.