Reduced Workers’ Compensation Costs 

With Roof Screening 

Jonisha P. Pollard, Susan M. Moore & Christopher Mark 

Abstract 

Each year, more than 300 underground coal miners are 

injured or killed by rocks falling from between or around 

roof supports. Researchers have reported that a reduction in rock fall injuries by implementing wire-mesh roof 

screens would reduce a mining company’s workers’ 

compensation (WC) premiums and would offset the annual 

cost of screen installation. However, the authors calculated 

these savings using formulas that are not used by all coal 

mining states, including Pennsylvania. Pennsylvania coal 

mines may also benefit from reduced WC premiums with 

roof screening. 

In this paper, the potential savings in WC premiums that 

could be achieved due to a reduction in rock fall injuries 

after roof screening in Pennsylvania’s underground coal 

mines were quantified. Hypothetical mines (representing 

two mine sizes: 67 and 150 employees) were constructed 

with realistic estimates of injuries and WC premiums. 

Using the Pennsylvania Coal Mine Compensation Rating Bureau’s (PA CMCRB) formulas, total savings in WC 

premiums after a 3-year period were determined. Savings 

in WC premiums ranged from 5.1% to 22% when injuries 

were reduced by 10% to 30%. This translated to savings 

between $73,000 and $1.2 million, which may largely offset 

the annual cost of a roof screening program. 

More than 300 rock fall injuries are reported to the 

Mine Safety and Health Administration (MSHA) 

each year. Nearly all of these injuries, which in

cluded six fatal injuries between 2006 and 2008, are caused by 

rocks falling between and around roof supports. Technology 

is available to prevent the vast majority of these injuries and 

fatalities. Surface controls like straps, headers and large roofbolt plates can help, but by far the most effective prevention 

technique is roof screening. Roof screens work best because 

they can cover up to 94% of the roof (Robertson, et al., 2003). 

Roof screens also offer a first line of defense for roof-bolter 

operators by confining or deflecting small rocks that can come 

loose during drilling or bolt installation. 

Several studies have now shown that roof screening is the 

most effective way to prevent rock fall injuries (Molinda & 

Klemetti, 2008; Compton, et al., 2007). At a Maryland mine 

studied by the National Institute for Occupational Safety and 

Health (NIOSH), rock fall injuries were reduced from 14 per 

year to 2.2 per year, 5 years after implementing roof screening. 

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In addition, an Illinois mine showed a reduction from 8 to 0.25 

injuries per year, 8 years after implementing roof screening 

(Robertson, et al., 2003). Despite the fact that roof screen

ing has obvious benefits to the safety of mine workers, some 

mining companies have yet to implement this safety measure 

due to cost concerns. However, by preventing injuries to the 

mine workers, roof screening has a direct positive impact on a 

mine’s WC premiums. 

Background 

Previous research has demonstrated that the savings in WC 

premiums may largely offset, or even exceed, the direct costs of 

a roof screening program. Moore, et al. (2010) determined sav

ings in WC premiums associated with reducing rock fall injuries 

in Illinois and Kentucky. Moore selected these states’ programs 

for evaluation because they have the highest WC premiums 

for underground bituminous coal, and the rating organization 

responsible for these states (National Council on Compensation 

Insurance) provides services to some 36 states. Moore’s analysis 

illustrated a decrease in WC premiums ranging from 1.8% to 

14.6% when injuries were reduced by 10% to 20%. 

The state of Pennsylvania, however, is not serviced by the 

National Council on Compensation Insurance, but rather has 

its own WC rating organization for coal mining and, thus, its 

own unique formula to evaluate mines within its borders. In 

2008, Pennsylvania’s bituminous coal mines produced 63.7 

million short tons of coal representing 16.3% of the total coal 

produced in the Appalachian Region (USEIA, 2010). 

Given Pennsylvania’s unique rating equations, it is im

portant to verify that a reduction in a Pennsylvania coal mine 

company’s WC premiums due to roof screening may partially 

or fully offset the cost of screen installation. Therefore, this 

research sought to quantify the potential savings in WC premi

ums that mining companies in Pennsylvania might expect after 

implementing roof screening as a method of reducing rock fall 

injuries. These savings could then be used to offset, or cover 

completely, the cost of implementing a roof screening program. 

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Overview of Workers’ Compensation 

Rate-Setting Methods in Pennsylvania 

Coal mines in Pennsylvania are rated by the Coal Mine 

Compensation Rating Bureau (CMCRB) of Pennsylvania. 

Insurance providers offering coverage for coal mines in Penn

sylvania must be a member of CMCRB. Several rating plans 

exist, including manual rating, merit rating and experience 

rating. Manual rating is the simplest rating plan where rates are 

averages reflecting the normal conditions found in each clas

sification and is typically used for small employers. 

Merit rating plans were formulated for smaller companies 

and provide a 5% premium credit to employers with no losttime accidents over a 2-year period. Employers with two or 

more lost-time claims receive a 5% surcharge and those with 

one lost-time claim have no change in premium. This plan pro

vides premium savings for safety-conscious small businesses. 

Under an experience rating plan, a company is provided an 

incentive (i.e., decreased costs) for implementing loss preven

tion programs to decrease injury costs. Any entity or company 

with a modified payroll of at least $300,000 during the 3-year 

experience period qualifies for an experience rating. Of the 

plans described, experience rating is the most commonly used 

and, therefore, is presented in this paper. 

Each year, data are collected by CMCRB for each individ

ual coal company. These companies are categorized by one of 

10 possible classifications: 

1) preparation plants—anthracite; 

2) preparation plants—bituminous; 

3) underground—anthracite; 

4) underground—bituminous; 

5) surface—anthracite; 

6) surface—bituminous; 

7) cogeneration fuel—anthracite; 

8) cogeneration fuel—bituminous; 

9) auger; 

10) coke. 

CMCRB then sets a base loss cost rate (per $100 of pay

roll), which must be approved by the State Insurance Com

missioner’s Office. The base loss cost rate consists of three 

components: 1) federal black lung coverage (FBLC), 2) state 

black lung coverage (SBLC) and 3) traumatic coverage (TC) 

(PA CMCRB, 2009). 

Based on a mine company’s 3-year injury history, a modi

fication factor (MOD) is calculated. (For a detailed explana

tion of determining the MOD and the use of the Pennsylvania 

WC rate-setting equations, see Moore & Pollard, 2010.) The 

MOD is the only factor that an individual mine can influence 

to reduce its WC premiums. This MOD is calculated each 

year based on the previous 3 full-coverage years (e.g., the 

MOD for 2004 is based on the mine’s experiences between 

2000 and 2002; the MOD for 2005 would then be based on 

the mine’s experiences between 2001 and 2003). The MOD is 

then used to determine whether or not the mine is credited (has 

a decreased premium) or debited (has an increased premium) 

relative to the base loss cost rate. The MOD is based on the 

individual company’s losses. Therefore, reducing losses by 

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implementing safety and health interventions, such as roof 

screen, should reduce the MOD. It should be noted that the 

MOD is only multiplied by the traumatic coverage portion of 

the base loss cost rate and not the FBLC and SBLC portions. 

The federal and state black lung portions are static and remain 

unaffected by the company’s performance over the experience 

rating period. Additionally, each insurance provider applies its 

own multiplier to the base loss cost rate to cover administrative 

fees (e.g., taxes, overhead costs, costs associated with han

dling, settling and defending claims). Thus, a company’s WC 

premium per $100 of payroll would be determined as follows: 

WC premium = admin fee multiplier * (FBLC + SBLC + 

MOD*TC) 

Methods 

Data Used in This Study 

The rating period used for this study was 2001, 2002 and 

2003, yielding WC costs for 2005. To demonstrate the expected 

amount of savings in WC premiums, hypothetical mines were 

created that are representative of experience-rated mines in 

Pennsylvania. Between 2001 and 2003, there was an average of 

44 active underground bituminous coal mines reporting pro

duction in PA with an average of 98 employees per mine (PA 

Department of Environmental Protection, 2001-03). Two sizes 

of mines were used in the analysis, one with 67 employees and 

the other with 150 employees. A mine with 67 employees was 

chosen because an economic analysis was previously conducted 

to determine the cost of screening for a mine of this size (Comp

ton, et al., 2007). The mine with 150 employees was chosen as 

a larger mining company with a significantly higher payroll. To 

estimate the savings in WC premiums for these mines, the fol

lowing parameters were necessary: 

•payroll for 2001, 2002 and 2003;

•total number of injuries each of the 3 years;

•number of injuries that would have been prevented by

implementing roof screening each of the 3 years; 

•base loss cost rate in 2005;

•insurance provider’s administrative fee;

•ultimate losses associated with each injury.

In 2005, the base loss cost rate was $25.30 for bituminous, 

underground coal mines. In Pennsylvania, typical multipliers 

applied by insurance providers to cover administrative fees 

range from 1.17 to 1.60; the average of these numbers, 1.385, 

was used in this study. To obtain the remaining parameters, 

several assumptions were made: 

•Payroll: In 2002, the average mine worker salary in Penn

sylvania was $53,700 (U.S. Census Bureau, 2002). This salary 

was used to estimate the salaries in 2001 and 2003 by adjust

ing for 1.14% inflation between 2001 and 2002 and 2.60% 

inflation between 2002 and 2003 (Bureau of Labor Statistics, 

2001-03). The average mine worker salaries were determined 

for 2001 as $53,094 and for 2003 as $55,096. The total payroll 

for a 3-year period was used to determine the MOD. There

fore, the total payroll for each year was summed to yield a 

3-year payroll. 

•Total number of injuries: A sensitivity analysis was 

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performed where the total number of injuries was varied to 

determine its effect on WC premiums. Over the 3-year period, 

the total numbers of injuries at both mines were defined as 

being 30%, 50% and 70% of the number of employees. These 

percentages were based upon actual injury data reported to 

MSHA during the same timeframe. 

•Number of preventable injuries: A sensitivity analysis 

was performed where the number of preventable injuries is 

varied to determine the effect of reducing rock fall injuries on 

WC premiums. The total number of injuries that could have 

been prevented with roof screening was defined as being 10%, 

20% and 30% of the total number of injuries. These percent

ages were based upon actual injury data reported to MSHA. 

(Injury narratives were read to determine the number of rock 

fall injuries and the size of the rocks associated with these inju

ries. The “preventable falls” were small falls and their general 

size was described in a variety of ways, including as the size of 

a golf ball, a “piece of rock” or in specific dimensions, such as 

18” x 18” x 8”, 4’ x 3’ x 1”, 3’ diameter x 8”, 2” x 2’, 2” x 9” 

x 2’ or 6” x 6” x 2”.) 

•Ultimate losses per injury. CMCRB provided the total 

ultimate losses and total number of medical and indemnity 

claims during the 2001-03 policy years. Indemnity claims are 

associated with claims resulting in lost-time. Medical claims 

are those where costs are exclusively medical. On average, 

two thirds of all claims each year were medical claims with 

an average cost of approximately $5,000. The average cost 

of indemnity claims ranged from approximately $40,000 to 

$55,000 depending on the year. 

Thus, to arrive at a representative average claim cost, it was 

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not reasonable to 

divide the ultimate 

losses by the total 

number of claims. 

Therefore, an average 

claim cost was calcu

lated for each year. 

The average cost of 

medical claims was 

multiplied by the 

number of medical 

claims reported, and 

the average cost of 

the indemnity claims 

was multiplied by the 

number of indemnity 

claims reported. This 

allowed the aver

age injury costs to 

be weighted based 

on their frequency. 

The average of these 

parameters across 

the 3 years was then 

determined to be 

$15,109. In the cur

rent analysis, there

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fore, every injury was assumed to cost this amount. 

Nine hypothetical mines were created, each with 67 em

ployees, such that a mine existed representing all possible 

combinations for the total number of injuries (30%, 50% and 

70% of the number of employees) and the total number of 

preventable injuries (10%, 20% and 30% of the total number 

of injuries). Similarly, nine hypothetical mines were created 

with 150 employees, yielding a total of 18 hypothetical mines 

in this analysis. 

Results 

The demographics and injury statistics associated with each 

hypothetical mine are shown in Table 1. 

Table 1. Demographics of each hypothetical mine.
 

The total injuries 

across the 18 hypothetical mines ranged from 20 to 105 in

juries, of which 2 to 32 were assumed to be preventable with 

roof screening. The total injury payout per year ranged from 

$303,694 to $1.6 million. Table 2 shows the MODs and result

ing WC premiums for each of the 18 hypothetical mines with 

and without roof screening. Additionally, the expected savings 

in WC premiums, which may be achieved with roof screening, 

are also provided. Almost all mines had MODs greater than 

1, which indicates that most mines were debited and were ex

pected to pay above the base loss cost rate. The MODs ranged 

from 1.21 to 2.15 before roof screening and 0.99 to 1.99 after 

roof screening. This reduction in the MOD yielded savings in 

WC premiums of $73,000 to $1.2 million. 

Figure 1 (p. 28) shows the percent savings in WC premiums 

for each of the hypothetical mines. Savings in WC premiums 

ranged from 5.1% to 22%. Additionally, Figure 2 (p. 29) 

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shows the savings in WC premiums associated with a decrease 

in ultimate losses. Although not a 1:1 ratio, savings in injury 

claim costs result in large savings in WC premiums. 

Table 2. MOD and associated WC premiums with and without roof screening showing savings. Note: *Savings in WC 

premium may fully cover the cost of roof screen installation assuming roof screening costs $240,000 and $480,000 for the 67 

and 150 personnel mines, respectively (Compton, et al., 2007). 

Discussion 

In this study, the methods used by the state of Pennsylvania 

to determine an underground bituminous coal mine’s WC pre

miums were also used to determine the savings in WC premi

ums that may be realized after reducing the number of injuries 

with roof screening. A sensitivity analysis with 18 different 

hypothetical PA underground bituminous coal mines was 

performed. In this analysis, the number of total injuries and the 

number of injuries that could have been prevented with roof 

screening were varied to determine their effects on a mine’s 

MOD and, therefore, WC premium. 

This analysis was completed for a medium-sized mine (67 

employees) and for a larger mine (150 employees). The reduc

tion in losses associated with roof screening was shown to 

decrease the MOD in all cases. While reducing actual losses by 

a set dollar amount does not directly correspond to the expected 

reduction in WC premiums, a significant savings in WC premi

ums is passed on to the mine. These savings ranged from 5.1% 

to 22% when injuries were reduced by 10% to 30%. For mines 

with a larger number of employees, and thus a larger payroll, the 

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percent savings in WC premiums was slightly greater than that 

of a smaller mine with a similar percent reduction in injuries. 

The savings after reducing injuries with roof screening may 

largely offset, if not cover completely, the cost of implementing 

a roof screening program. Compton, et al. (2007) determined 

the cost of roof screening for a room-and-pillar mine employing 

67 people and producing 800,000 tons per year. If roof screens 

were installed in 50% of the drivage, the annual cost for screen 

installation was estimated to be $240,000. This cost varies 

between mines but provides a relative estimate for the expected 

cost of screen installation. Based on this estimate, several of the 

67-employee hypothetical mines in this study would cover the 

cost of their roof screen program solely from savings in WC 

premium. 

It is important to note that mines with greater rock fall 

injuries will see more substantial savings in their premiums. 

The size of the mine (determined by their payroll) determines 

their expected losses (injury costs expected for a mine of that 

size) and the premium paid to the WC insurance provider (WC 

premiums are relative to every $100 of payroll). However, the 

actual losses at the mine influence how much the mine will pay 

in premiums. This means that a larger mine with fewer injuries 

may actually have a lower WC premium than a smaller mine 

with more injuries. 

There were several limitations to the current study. The 
mines in the study were hypothetical as opposed to using real 

mine demographic and injury data. The total number of injuries 

and the preventable injuries at each hypothetical mine were 

based upon injury data obtained from the MSHA injury data

base. As a result, mines of comparable size may have more or 

less savings depending on their actual injury records and roof 

control plans. 

Figure 1. Percent savings in WC premiums associated with 10%, 20% and 30% reductions in injuries due to implementing roof screens for mines with total injuries equal to 30%, 50% and 70% of the number of employees. The number of 

employees was set to equal either 67 or 150. 

Another limitation to the study was that an average injury 

cost was used instead of determining the true injury costs asso

ciated with known injuries at a specific mine. The estimated cost 

for installing roof screens presented in this study ($240,000) 

was associated with only one mine of 67 employees; however, 

this cost estimate was based on an actual mine providing them 

more validity than a hypothetical estimation of costs. 

Finally, it should be noted that large coal companies tend to 

purchase nonstandard WC policies. Specifically, there would 

be some type of risk-sharing policy, such as a large deduct

ible or the mining company may be self-insured and have 

purchased an excess WC policy. For the latter case, the cost 

associated with every claim eliminated through roof screening 

is directly saved by the company; additional savings would 

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then be observed by the reduction in the MOD associated with 

the excess WC policy. 

The data presented in this study demonstrate that a savings 

in WC premiums may be expected after roof screening for a 

3-year period. This means that companies may not fully benefit 

from reduced injuries until 5 years after instituting their safety 

measures. However, some financial benefits may be seen after 

3 years. While the hypothetical mines used in this sensitivity 

analysis were only PA mines, the results are comparable to 

those obtained in a similar study, which investigated the poten

tial savings in WC premiums for states using a different, and 

more commonly implemented, experience rate-setting formula 

(Moore, et al., 2010). 

While the savings in WC premiums are less than the value 

saved in direct injury costs, the savings are still substantial. 

Results of this analysis showed a linear relationship between the 

decrease in ultimate losses and the savings in WC premiums. In

jury costs are directly proportional to WC premiums, and imple

menting safety measures to reduce injuries may be financed by 

the potential savings in WC premiums alone. 

Roof screening allows mines to provide up to 94% roof cov

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erage and, therefore, reduce the potential falls of smaller rocks, 

which cause about 99% of all rock fall injuries (Robertson, et 

al., 2003; Molinda, et al., 2002). Considering the obvious safety 

benefit of using roof screen, some mines still do not implement 

a roof screening program. Barriers for screen installation include 

material costs, time for installation and possible ergonomic risks 

to the operators (Robertson & Hinshaw, 2002). NIOSH studies, 

including this analysis, have examined all of these barriers and 

recommendations are provided for alleviating these concerns. 

Moore, et al. (2010) found significant savings in WC premiums 

after roof screening in Illinois and Kentucky underground bitu

minous coal mines. The results of their analysis were in agree

ment with this study in that many mines may fully cover the 

cost of roof screen installation with savings in WC premiums. 

Figure 2. Savings (in thousands of dollars) in WC premiums associated with decreased 

ultimate losses (in thousands of dollars) after roof screening.

In a case study of four underground coal mines, the addi

tional material costs and time associated with roof screening 

were examined (Robertson & Hinshaw, 2002). Authors found 

that the material costs for roof screening resulted in an extra 

$0.58/ft when used instead of steel straps and significantly 

increased roof coverage by 61%. A significant variation in 

the additional cycle time required for roof screening was seen 

between the four mines, and the authors noted that some of 

this time may be reduced with time and practice. In general, 

the use of a bolting machine with a built-in materials handling 

system was shown to decrease the necessary cycle time. The 

authors also noted the concern with sprains and strains as

sociated with manually handling roof screens and stated that 

“any innovations in bolting machines, supplies or processes 

that could eliminate or reduce material handling are worthy of 

consideration for the safety of the workforce.” 

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In a later analysis, Comp

ton, et al. (2007) conducted 

ergonomic analyses of roof 

screen handling techniques. 

Subjects manually handled 

roof screen while instru

mented with devices to 

measure the muscle activ

ity of the arms and torso 

and trunk position, velocity 

and acceleration. Results 

showed reduced demands 

and decreased cycle time 

when roof screens are slid 

along rails mounted on top 

of the roof bolter. The au

thors also suggested storing 

screens on the mine rib or 

stacked/stored on the rails 

mounted on the roof bolter 

to reduce the risk for back 

injuries. 

Roof screening has been 

proven to be a successful 

means of reducing the haz

ards of working under a coal 

mine roof. NIOSH research

ers have examined the roof 

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screening process in hopes of alleviating the concerns with 

increased material costs, cycle times and risks for materials 

handling injuries. Researchers have found the effects of roof 

screening to result in financial savings that may recoup some 

(if not all) of the costs of installation. 

WC premiums are just one of the financial savings that may 

be realized with roof screening. The actual cost savings to the 

mine are expected to be greater than that which has been esti

mated using the method described in this paper. Other savings 

include reduction in costs associated with replacing injured 

workers, reduced requirements for extra spot bolts to support 

loose roof and reduced costs associated with long-term cleanup 

and resupport (Compton, et al., 2007). Moreover, production 

rates are often impacted by nontangibles, such as increased 

employee morale, positive safety culture, maintenance of a 

consistent, knowledgeable workforce, etc., which exist when 

safety is made a priority, hazards are removed and injuries are 

reduced or eliminated. x

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