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This may be because most mines are accessed through flat alleys rather than shafts, so the depth is difficult to determine. The report provides information on the thickness of the coal seam, which represents a further cost.
In fact, seam thickness may be a determinant of productivity In our main sample, the correlation between seam thickness and productivity is 0.38 (which is the highest correlation between our explanatory variables). We will consider the implications of this link in section III. Seam thickness may change over time, possibly due to changes in the seam within each mine (as shown in the data). Finally, time-to-year, annual effects will be included in all specifications as an alternative to reducing the cost of mechanical ventilation. A potential limitation of our model is that we do not consider unionism to be a factor in the adoption of mechanical ventilation. Boal, based on estimates of unionization from collected data, shows that unionized mines tended to reduce mortality, especially in the period 1897-1913.
However, given the difficulties workers faced in organizing in the early days, the level of unions during our study period tended to be low: 0% before 1901, 6.5% in 1902, and about 13% thereafter. In fact, based on the complaints recorded by inspectors about the furnace by miners, they may have preferred more powerful ventilation technology. To consolidate the results, our empirical analysis will include a series of robustness checks. The results of the new technology adoption model. Average marginal effects were reported. The estimated coefficients for all variables are significant at normal levels, with seam thickness being the main exception. The signs are also consistent between different estimates.
In CRE estimates, the time mean of the explanatory variables (i.e., the fixed effect produced) is uninterpretable and therefore not reported. The size of the estimated coefficients for all variables is small – once the resulting fixed effect is added. Regarding the variables reflecting benefits, in column 5, identifying mines as gas-bearing increases the likelihood of fan adoption by 28%. It is most likely no accident that mine owners react decisively to this factor. The inspectors clearly and repeatedly stated their view that mechanical ventilation is the best way to deal with clear hazards such as biogas.
"In mines with biogas, the fan is significantly better than the furnace fan and the current generated by the furnace is more regular than the current generated by the furnace". Another inspector, referring to the law allowing ventilation to be fully turned on, explained that furnaces that produce explosive gases in mines are known to be a source of danger and furnaces are very unreliable sources of ventilation". Each explosion in the previous year increased the likelihood of adopting a fan by 14 percent. In addition, in the unreported specification, the binary variable that is an alternative to the number of explosions is not important. The additional lag of the explosive variable also showed no effect. At first, the difference between the "potential" effects of biogas and the "real" effects of explosions can be staggering.
However, as mentioned above, an explosion turned out to be a fairly rare event, perhaps no more expensive than installing mechanical ventilation. In addition, mine owners blame carelessness in various tasks as a factor in the explosion discussion, diverting attention from expensive investments in safety equipment, and as expected, the scale of operations, represented by the number of workers, also affects fan use. Larger mines require more powerful ventilation technology. The interaction shows that the influence of mine size does not really depend on the presence or absence of biogas. In addition, the unreported specification, which uses coal tonnage in coal mines as an alternative measure of operating scale, provides similar to the table — except for the productivity variable, which may be highly correlated with coal tonnage in coal mines, 0.55. The share of machine mining output also has a positive and significant impact on the adoption of mechanical ventilation.
This result shows the importance of the risks posed by early and rapid mechanization. As for the cost variable, productivity also had a positive and significant impact on the use of mechanical ventilation. This result seems to confirm the relationship between productivity and the ability to finance new technologies. The seam thickness does not show the effect. In additional, unreported regression, we removed seam thickness and found that the productivity variable and other variables had essentially the same results. Finally, unreported time-year effects tend to show an increase in the magnitude of their positive effects—becoming significant from 1903 onwards.
Therefore, this result suggests that mechanical ventilation may become more affordable over time. Reasonable attention to our results is associated with the nature of the sample, a group of matching mines appeared for at least two years during this period. Therefore, we first considered a series of samples to minimize the possibility of deviations: we replaced the main samples with a new, restricted mine sample that reported all years between 1898 and 1907, meaning that they continued to operate throughout the period; We used a sample in which "already processed" cases, that is, those mines that were mechanically ventilated in all the years in question were removed. We did this to rule out any possibility that already treated cases may have improved the accuracy of estimates; We added mines that were reported only once to get a larger pool – a robustness check that resulted in our focus on mines that were reported only once.
In the other two samples: e) we added (previously excluded) nine mines that switched from mechanical ventilation to furnace ventilation; and (f) we removed one observation year, corresponding to the Monongah 6 & 8 mine explosion – an outlier in terms of its size. Unreported results are similar to those shown in the table, with the main exception being that the number of explosions was of little significance or only one in the mine sample reported in all years, probably because of their small size. Here, we first estimate a linear probabilistic model, a reasonable complement to the binary response of estimating the logical model, and due to its inherent complexity, we then estimate the time to adopt the model. Specifically, the model, which makes no assumptions about the shape of the "hazard" function (the probability of mechanical ventilation in the mine).
The results tend to be similar, with the main exception being the weaker significance of the explosion variant. The possibility of adopting fans may also be influenced by the location of the mine within the coal basin, for example, due to the relative enthusiasm of inspectors in promoting mechanical ventilation. When we take this into account, the primary results are also robust through multi-level models that include changes at the county level. Our main model estimates are based on the choice between two options: mechanical ventilation versus all other available methods, basically furnace and natural. In the early days of our study, natural ventilation was already relatively unimportant (24% of mines in 1898), and by the later stages (10% in 1907), in fact, inspectors recommended natural ventilation only in "exceptional circumstances", usually referring to very small or short-lived mines.
In any case, we estimate a polynomial logit model to reduce the assumption that other methods (melting pot and nature) can be placed in the same category. However, in terms of the symbol and importance of the variables, there is essentially no difference between natural ventilation and furnace ventilation compared to mechanical ventilation. Finally, our approach has so far alleviated some endogenous problems, as the conversion of ventilation systems has only been observed in... After that, the characteristics of the mine were determined. Still, it leaves the question of how mines, originally classified as fan-ventilated, decided on this approach in the first place.
For many mines, there is no statistical way to answer this question because we have no way of knowing how old the mine is or when it installed a fan. But there is one special case that solves the problem of initially choosing fan ventilation: the newly sunken mine. If we are willing to assume that the survey is complete (a bold assumption, of course), then the mines that appear in the time t survey but do not appear in time t-1 must have been opened during this time. We can ask: what features of these mines are related to the immediate installation of mechanical ventilation? The specifications for this type of mine are consistent with those in the table. The low significance of the number of explosions makes sense because there is no lag in this variable. Our key specifications and robustness checks show that mechanically ventilated mines tend to be filled with biogas, have exploded, are larger, more mechanized and more productive. An additional estimate5 (column 1) is reported in the table, indicating that the installation of fans actually reduced explosions, thus confirming the validity of the inspectors' recommendations.
The Poisson coefficient for the previous year's fan meant that the expected number of explosions was about 100 (e.g., −1.083)-1) ≈ 66% lower. However, older furnace methods are still common in coalfields at the end of the period we cover. In this section, additional evidence is supplemented by cost-benefit explanations for the persistence of earlier technologies. Furnaces are sometimes more popular than fans because their replacement has three costs associated with them. First, despite the guidance of inspectors, for some owners, they may be making decisions when information about the advantages of the latest technology is still relatively limited. On the contrary, there is a great deal of knowledge and experience about old technologies. How much air per unit time is a fundamental factor to consider, however, until the turn of the century, fans were not always more mechanically efficient than furnaces.
Experiment-based evidence from several countries (although difficult to compare) points to the late nineteenth century as the time when furnaces reached their peak efficiency and mechanical fans increased their efficiency, due to the introduction of more advanced fans, such as the increasingly popular Gibal and Capel designs in Europe and the United States, and second, furnaces often cost much less to install than fans. Through multiple sources, we were unable to find quantitative evidence of the cost of wind turbine installation in the West Virginia coalfield, with one exception. This estimate is placed with estimates of richer ventilation methods from European sources. The word "fan" refers to the Gibal and Capel types – the most commonly used types in West Virginia. Most of the estimates of furnace installation costs come from the UK, where this (lesser) type of information is more readily available, and West Virginia mine owners estimate a fan at around $8,000.
For further reference, in West Virginia, the average annual salary per gathering miner is $643.05. Therefore, the initial cost can be a heavy burden for the average West Virginian, and the small size of the West Virginia Coal Mine inspector believes is a major cost factor for the adoption decision. For example, in a mine, "a fan is considered a better (than a stove) means of ventilation", but "the cost of one fan is considered unreasonable (by the mine owner)". Since rural West Virginia doesn't have access to purchased electricity, the need to build a power source may also be one of the reasons.
If the first cost of installing a fan could be as cheap as many makeshift furnaces, I am satisfied that there would not be a single mine without a fan in this country." Finally, miners may also face a high degree of uncertainty in the use of new technologies and therefore continue to use furnaces in some cases.