In this study, a formula called the Golden Index was developed that calculates a value for each player according to their individual and collective performances. This method identifies the most important players, designated as Golden Players, in football attacking plays. This study was organized in two main phases: (1) selection, definition and validation, including weighting assignment, of a set of variables associated with players’ performance through application of statistical techniques to uniformize variables values that compose the Golden Index formula and (2) applicability of the Golden Index formula to quantify players’ performance of Club Atlético de Madrid over 2016-2017 season. A questionnaire was given to football experts in order to validate and determine the weight of each of the 12 variables selected. Descriptive statistics with standardization techniques were used to set the weights and uniformize each variable of the Golden Index formula. Applying the Golden Index formula to Club Atlético de Madrid 2016-2017 season named Koke, Yannick Carrasco and Filipe Luís as the Golden Players, while the centre-backs Lucas Hernández, Stefan Savić and Diego Godín and striker Fernando Torres received negative indexes. Results suggested that the Golden Index formula is a valuable and useful tool in capturing the individual and collective performance of players in attacking play in football.

IntroductionSuicide is a serious public health problem, being the second leading cause of death among 15–29-year-olds. Many risk factors have been associated with suicidal behavior, such as psychiatric disorders, family history of suicide, loss of a close friend/relative, physical/sexual abuse, lack of support network, or sleep disturbances where nightmares and insomnia have been consistently reported to increase the risk of suicidal behaviors.ObjectiveTo conduct a systematic review to examine the association between short sleep duration and suicidal behaviour (suicide ideation/attempt/suicide).MethodsThis is a systematic review of published research articles in the electronic database PubMed in the last 10 years. The query “sleep” or “sleep disorders” and “suicide” was used. Studies that assessed the relation between sleep duration and suicidal behaviour, with a well-defined index for sleep disorders and with an outcome measure of suicidal behavior were included.ResultsOf the 522 references founded, 33 articles met the inclusion criteria (1 review, 1 qualitative and 31 quantitative studies). An association between short sleep duration and suicidal behaviour was found in most of the studies with children/adolescents and adult samples. However, this relation was not verified in the research into the elderly.ConclusionThe results point to a significant association between short sleep time and the presence of suicidal behaviours, for both adults and children/adolescents. The effect of short sleep duration seems to be more consistent with suicidal ideation, but not for attempts, needing further studies to highlight the importance of this link between sleep duration and suicide.Disclosure of interestThe authors have not supplied their declaration of competing interest.

This paper studies the post-IPO operating performance of a sample of 555 European firms that went public between 1995 and 2006. Consistent with previous findings, we observe a decline in post-issue operating performance of IPO firms. However, firms located in emerging European countries perform even worse after the IPO than firms located in developed European countries. Our results suggest that this less successful post-issue operating performance by firms located in emerging countries can be explained by a more aggressive use of accruals and a better timing of the IPO in order to coincide with a period of high operating performance.

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