{'fraction_non_alphanumeric': 0.019817287420941673, 'fraction_numerical': 0.06598735066760365, 'mean_word_length': 4.607171000788022, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
A study of the correlation between seniority and the number of work accidents in mining enterprises between 2003-2017

A work accident comprises a number of interrelated adverse technical, organizational, environmental, and human events. However, it has been claimed that the main contributing factor responsible for work accidents is a human error (disruption). The causes of human errors may include: incapacity, nature of tasks being performed as well as physical and social environment. It is important to note that the first element is strongly related to both age and seniority. Based on available literature, the impact of seniority on work accidents is not clearly defined. Advanced age of employees favors the acquisition and consolidation of professional knowledge, but it can also be associated with greater automation of behaviours in work environment. This can lead to an error resulting in a dangerous situation or accident. Bearing in mind the above, this study examined the relationship between seniority and the number of work accidents among individuals employed in mining enterprises. The study was carried out using the Pearson’s correlation coefficient. The source of analysis included statistical data on the size of employment in individual seniority groups and the number of work accidents in mining enterprises between 2003-2017. The research showed a correlation between age and the number of work accidents in hard coal mines.


Introduction
A work accident can be defined as a sudden work-related event caused by an external factor that leads to an injury or death of an employee. However, in the theory of causality of work accidents and related preventive occupational safety and health (OSH), this definition has changed -from accidents regarded as "accidental events or the effect of unpredictable force majeure" to "an accident model as a consequence of errors made due to the deficit of motivation, knowledge and experience of employees" [1]. This change prompts research on the prevention of accidents not only in the technical sphere, but also in areas like management and motivation, proper training, information flow, evaluation or analysis of the psychophysical features of employees and their adjustment to a workplace [2,3]. This is particularly necessary in a situation where, according to long-term statistical data provided by GUS, around 60% of work accidents in Poland are caused by the so-called human factor.
Progressive changes in the demographic structure of developed countries observed for many years have caused increasing disproportions in the workforce age distribution. Every year, the number of older employees is reported to be increasing as opposed to the number of younger employees, which is decreasing. This affects the sphere of OSH. A work accident comprises a number of interrelated adverse technical, organizational, environmental, and human events. However, it has been claimed that the main contributing factor responsible for work accidents is a human error (disruption). The causes of human errors may include: incapacity, nature of tasks being performed as well as physical and social environment. It is important to note that the first element is strongly related to both age and seniority.
Extensive work experience is associated with higher effectiveness. Longer seniority favors the acquisition and consolidation of professional knowledge, but it can also be associated with greater automation of behaviors in work environment. This can lead to an error resulting in a dangerous situation or accident. Bearing in mind the above, this study examined the relationship between seniority and the number of work accidents. The source of analysis included statistical data on the size of employment and the number of work accidents in mining enterprises.

Seniority and accident rates
Based on available literature, the impact of seniority on work accidents has not been explicitly defined. On one hand, many studies show that greater work experience leads to a smaller number of work accidents due to better knowledge of procedures, regulations, occupational safety policy, and skills to cope with emergency situations [4,5,6,7,8]. On the other hand, other studies indicate that the longer seniority, the lower physical fitness, work efficiency, and, above all, the perception of threats. This may result in higher work accident rates at higher seniority levels and more serious consequences [9,10]. Also, employees with shorter seniority often lack life and professional experience, which makes them more exposed to work accidents and less aware of the consequences of dangerous behaviors [11]. It is important to note, however, that the same employees do not fall into a work routine, and can perceive risks more effectively.
With regard to the foregoing, the relationship between seniority and work accidents is a very complex issue, which prompted the author of this study to conduct research in this area based on mining enterprises.

The number of work accidents versus seniority among individuals employed in mining enterprises -presentation and research analysis.
The statistical data from 2003-2017 were used to analyze the relationship between changes in the number of employees in given seniority groups and the number of work accidents in mining enterprises [12,13].
The study was carried out using the Pearson's correlation coefficient. This coefficient is used to study the linear relations of studied variables, in which an increase in the value of one characteristic causes proportional changes in the mean values of the other characteristic (increase or decrease). Poor or lack of relationship occurs at values below 0.2.
Correlation (interdependence of features) defines interrelations between selected variables. Here, values are accepted when in the range between -1 and 1. Positive correlation (correlation coefficient from 0 to 1) informs that an increase in the value of one characteristic is accompanied by an increase in the mean values of the other characteristic. Negative correlation (correlation coefficient from -1 to 0) informs that an increase in the value of one characteristic is accompanied by a decrease in the mean values of the other characteristic. If a given correlation coefficient is negative, it may be claimed that when the values of one variable increase, the values of the other variable decrease, and the other way round. Based on the analysis of the seniority structure in mining enterprises between 2003-2017 (figure 1), the seniority group dominating for many years was the one between 16-25 years of service. When considering the time at which workers employed underground currently reach the retirement age (after 25 years of work), it can be concluded that the dominant seniority group includes employees approaching their retirement age. As the research shows, employees in the lowest seniority groups constitute a very small group that failed to satisfy the competency needs of their companies when the natural wastage, such as retirement, occurred. However, in recent years, positive changes in the seniority structure can be noticed, including an equal share of groups of employees with different seniority in the total structure. This is a very positive trend that should be constantly studied and supported by a balanced employment policy in mining enterprises.  It is worth noting that in 2009, an increase in the total number of work accidents in mining enterprises was found, which coincides with a very large staff turnover in the previous year. According to the statistical data on mining industry, in 2008, almost 14,000 employees were dismissed, and more than 17,200 people were employed [13].  2003  2421  202  1267  6106  19699  32575  39450  24469  9449  2845  386  2004  2243  526  1125  5365  15856  29296  37151  24237  10061  2961  508  2005  2117  688  2130  4536  13704  27771  35935  24438  10611  3080  518  2006  2321  992  3647  3979  11409  24548  34997  24928  11205  3009  598  2007  2505  1623  6741  4486  9443  22292  32843  23858  11449  3029  642  2008  2552  3149  12187  6502  9420  20421  30215  22786  11133  3260  640  2009  2799  1330  14504  7405  8889  17837  28921  23456  11964  3818  751  2010  2056  1125  13583  8948  8194  15052  26660  22814  12468  4324  921  2011  1795  2357  15088  11870  8127  13438  23855  21934  11838  4696  1032  2012  1663  2248  16356  14773  8323  11639  22079  19810  11452  5271  1305  2013  1471  977  15024  16794  8614  10338  20030  17249  10578  5524  1565  2014  1379  685  12107  18605  9205  9829  17469  15554  9498  5857  1866  2015  1356  290  9528  17361  10960  9015  13808  13458  8097  5509  1898  2016  1247  860  7359  16624  12491  8485  11824  11250  6918  4847  1890  2017  1294  1417  7135  17209  14608  8293  10034  9714  6117  4361  1737  correlation  coefficient  0, The analysis of the relationship between data presented in figures 1, 2 and in table 1 on the seniority of individuals employed in mining enterprises and the work accident rates indicates a strong negative and positive correlation for 7 groups. The calculated Pearson's correlation coefficient is between -0.91 and 0.88.
When studying the results presented in table 1 for the years 2003-2017, a strong negative correlation can be noted between the characteristics in the seniority groups with 6-10 and over 36 years of service. This means that an increase in one parameter (the number of employees in mining companies) is accompanied by a decrease in the value of the other parameter (the number of work accidents). By contrast, a strong positive correlation can be observed between changes in the number of employees in the seniority group with 16-35 years of service and the number of work accidents. This means that an increase in the number of employees in this group of seniority is accompanied by an increase in the number of work accidents in subsequent years.
For a more in-depth analysis, below are presented 3 figures that show the following seniority groups compared with the number of work accidents:  0-10 years of service,  16-35 years of service,  36 and more years of service.  As can be seen from the statistical data presented in figure 3, there is a clear discrepancy in the trends of both studied values. Nevertheless, it is worth emphasizing that the total number of work accidents between 2003-2017 in mining enterprises is observed to decline. Also, the calculated correlation coefficient in the 1-5-year seniority group shows a weak negative correlation. On the other hand, for the seniority group with 6-10 years of service, a strong negative correlation was reported, i.e. an increase in the number of employees with this work experience is accompanied by a decrease in the number of registered work accidents. This is not the case, for example, when it comes to the seniority group with up to 1 year of service. Here, the correlation is very weak.

Conclusions
This study confirmed the existence of the relationship between seniority and work accidents, but at the same time indicated a large diversity of this relationship.
The results showed no correlations between the number of work accidents and the short (up to 5 years) seniority of employees in mining enterprises. Therefore, a theory that employees with short work service, and thus worse professional experience and knowledge of safe behaviors in work environment, are more likely to cause work accidents failed to be confirmed. Also, the research failed to find that the fluctuations in the number of employees in this seniority group could affect changes in the number of work accidents in mining enterprises. The situation is similar in the case of the seniority group with 11-15 years of service.
A strong negative correlation was observed in the group with 36 and more years of service. It comprised very experienced employees who oftentimes had already reached the retirement age but were still working to complement the shortages of staff and offer their employers high professional competences. With the increase in the number of employees in this seniority group, the number of work accidents was observed to decrease. Perhaps, employees with such long work service, complement their declining functional capacity with high professional experience and a cautious attitude to both risks and threats. Similarly, a strong negative correlation was observed between the number of employees with 6-10 years of employment in mining enterprises and the number of work accidents. The increase in employment in this group was accompanied by the decrease in the number of work accidents in the studied years (2003-2017). These were employees who were already well acquainted with the specificity of work in hard coal mines, aware of threats, but still young and physically fit, which may have affected the lower accident rate in this group. What is more, the strongest positive correlation was demonstrated in the group with 16-30 years of service. The increase in the number of employees in this group of employees showed a strong correlation with the increase in the number of work accidents in mining enterprises. Therefore, professional experience that is said to grow with seniority, in the case of mine employees who have not yet reached the retirement age, failed to result in smaller accident rates in this group, but showed opposite effects. However, it does not seem to have been influenced by the lack of awareness of threats or the ability to cope with emergency situations. This result is probably due to the low culture of work safety in mining enterprises [14] and professional routine. It is worth noting that the number of work-related accidents reported in individual seniority groups could have also been impacted by the types of positions occupied by employees in various seniority groups. Employees with short seniority -inexperienced, were in positions often associated with a higher occupational risk compared to employees with longer work service. That is why, the results of this study should be taken into account when selecting employees for work positions, planning trainings and broadly understood accident prevention.