Development and Evaluation of 

Colorado’s Low Emitter Index

Colorado Department of Public Health and Environment

May 2007 

Prepared by: 

Mobile Sources 

Air Pollution Control Division

Colorado Department of Public Health and Environment

and 

Peter M McClintock, PH.D. 

Applied Analysis

891 Tiburon Blvd. 

Peter.mcclintock@comcast.net 
z Page 2 
Introduction 

Colorado’s inspection and maintenance (I/M) program includes a Clean Screen element that allows

vehicle owners the option of being exempted from their required I/M240 inspection, if their vehicle is

determined clean. Currently, to qualify as clean a vehicle must be seen by a Remote Sensing Device 

(RSD) a minimum of two times within 12 months prior to its required I/M240 inspection, with emissions

measurement less than 200ppm and .5% for HC and CO respectively. 

The Colorado Department of Public Health and Environment (CDPHE) is proposing to add a hybrid

method of identifying clean vehicles that combines a single clean RSD measurement with a Low 

Emitter Index (LEI) criterion. The LEI qualifies vehicles as Clean Screen candidates based on a 

historically low probability of emissions failure for similar vehicles. The addition of the LEI hybrid

method will increase the productivity of the existing Clean Screen program and allow more vehicle

owners to take advantage of the convenience of clean screening without jeopardizing the benefit to the

current I/M program. The LEI qualification criteria will be evaluated/updated on an annual basis to

ensure it is equal to or better than the current 2-hit clean screen program. 

Colorado’s I/M program is included in both the One Hour Ozone Maintenance Plan and Eight Hour

Ozone Early Action Compact (EAC), as a mobile source control strategy. The program as modeled

prohibits Colorado from evaluating more than 50% of the I/M eligible fleet. The inclusion of the

proposed LEI hybrid method will not exceed this threshold. 

This document describes how the LEI was developed along with the comparison of the projected

performance of the hybrid method to the current 2-hit Clean Screen method. 

Source Data and Vehicle Grouping 

An LEI lookup table has been developed using 2005 and 2006 initial IM240 inspection results. 

Colorado tests AWD and traction control vehicles on 4WD dynes so there are few models that do not

receive IM240. 

Vehicles are grouped using:

- Colorado1 Vehicle Type: LDGV, LDGT1, LDGT2, HDGT1, HDGT2 

- Model Year: the tenth character from the VIN 

- Make: decoded from the VIN; 

- Model: decoded from the VIN; 

- Engine Displacement: decoded from the VIN; 

Only groups containing 20 or more vehicles will be retained in the combined profile in order to avoid 

concerns over statistical variability in small sample sizes. Missouri had used the first five characters of 

the VIN in lieu of Make and Model. Colorado proposes using Make and Model as decoded from the 

VIN using the Polk program, since this approach appears to better and more consistently differentiate 

Make/Model than the Missouri approach. 

 1

 In the Colorado data, light trucks are defined using four types: LDGT1, LDGT2, HDGT1, and HDGT2. 

The first pair roughly corresponds to the EPA’s LDGT1 and the second pair corresponds to EPA’s

LDGT2. 

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Table 1 compares the use of alternative sets of LEI vehicle groupings. It shows the number of source

vehicles, the number of bins with 20 or more results, and the percentage of all source vehicles in these

classifications. Coverage of source vehicles is highest with the proposed scheme. 

Table 1 

LEI Vehicle 

Groupings

Vehicles >=20

Bins

HC/CO 

Fail % 

NOx

Fail % 

HC/CO +

NOx Fail % 

Fleet 

Coverage

% 

None (All vehicles) 1,557,509 N/A 2.67% 0.16% 2.83% 100%

Veh. Type, Model Year , First 5 

VIN Char., Polk Engine 

Displacement, # of Cylinders 

1,439,382 8,438 2.54% 0.16% 2.7% 92.4%

Veh. Type, Model Year , First 5 

VIN Char., Polk Engine 

Displacement

1,450,518 8,388 2.53% 0.16% 2.69% 93.1%

Veh. Type, Model Year , Polk 

Make, Polk Model, Polk Engine 

Displacement

1,476,842 6,817 2.58% 0.16% 2.74% 94.8%

The LEI table generated using 2005/2006 I/M test results will typically be applied to vehicles inspected

in 2007 and part of 2008. Colorado has a four-year exemption for new vehicles. Although some

inspections on these models are performed, the 2005/2006 inspection results may leave gaps in the 

profile for models that will be four-year old vehicles in 2007/2008, e.g. 2003 and 2004 models. The 

gaps will be filled to a large extent by assuming newer year vehicles, will perform similarly (or better) 

than the same model of an earlier year, for which performance statistics are available, e.g. 2003 and

newer Acura MDXs will perform at least as well as 2002 Acura MDXs.

LEI Emissions Performance 

The values listed below were computed for each vehicle group. The average excess emissions per 

vehicle are the sum of the vehicle emissions exceeding the Colorado standards divided by the number

of vehicles in the group. These g/mi values are usually small compared to g/mi standards because

most vehicles do not add any excess emissions and all vehicles are included in the denominator. 

- Initial tests 

- HC/CO fails

- HC/CO fail %

- NOx fails 

- NOx Fail % 

- Overall fail % 

- Average Excess HC g/mi per vehicle 

- Average Excess CO g/mi per vehicle 

- Average Excess NOx g/mi per vehicle 

The LEI clean screening effectiveness will be targeted towards the most critical pollutants by adjusting

the selection criteria. 

Figure 1A plots the cumulative percentage of excess emissions vs. the percentage of vehicles when 

LEI groups are ranked by tailpipe emissions fail rate. Figure 1B is the same chart with an expanded yaxis. These charts indicate when groups of vehicles are ranked by increasing tailpipe fail rate, groups 

containing 70% of the vehicles produce only 10% of the excess HC and CO and 30% of the excess 

NOx. Note that total excess NOx is small compared to excess HC and CO due to Colorado’s lenient

NOx standards.

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Figure 1A LEI Excess Emissions vs. % of Vehicles When Ranked by Tailpipe Fail Rate 

Indexed by Tailpipe Fail Rate

0%

20%

40%

60%

80%

100%

0 10 20 30 40 50 60 70 80 90

% of Vehicles

% of Excess Emissions

Excess HC%

Excess CO%

Excess NOx%

Figure 1B LEI Excess Emissions vs. % of Vehicles When Ranked by Tailpipe Fail Rate 

Indexed by Tailpipe Fail Rate

0%

5%

10%

15%

20%

25%

30%

0 10 20 30 40 50 60 70 80 90

% of Vehicles

% of Excess Emissions

Excess HC%

Excess CO%

Excess NOx%

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Figures 2A and 2B show the cumulative percentage of excess emissions vs. the percentage of vehicles 

when LEI groups are ranked by the fail rate for HC or CO. Seventy percent of the vehicles produce 8%

of the excess HC and CO. 

Figure 2A LEI Excess Emissions vs. % of Vehicles When Ranked by HC/CO Fail Rate 

Indexed by HC/CO Fail Rate

0%

20%

40%

60%

80%

100%

0 10 20 30 40 50 60 70 80 90

% of Vehicles

% of Excess Emissions

Excess HC%

Excess CO%

Excess NOx%

Figure 2B LEI Excess Emissions vs. % of Vehicles When Ranked by HC/CO Fail Rate 

Indexed by HC/CO Fail Rate

0%

5%

10%

15%

20%

25%

30%

0 10 20 30 40 50 60 70 80 90

% of Vehicles

% of Excess Emissions

Excess HC%

Excess CO%

Excess NOx%

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Figures 3A and 3B show the cumulative percentage of excess emissions vs. the percentage of vehicles 

when LEI groups are ranked by excess HC. Seventy percent of the vehicles produce 5% of the excess 

HC. 

Figure 3A LEI Excess Emissions vs. % of Vehicles When Ranked by Excess HC 

Indexed by Excess HC

0%

20%

40%

60%

80%

100%

0 10 20 30 40 50 60 70 80 90

% of Vehicles

% of Excess Emissions

Excess HC%

Excess CO%

Excess NOx%

Figure 3B LEI Excess Emissions vs. % of Vehicles When Ranked by Excess HC 

Indexed by Excess HC

0%

5%

10%

15%

20%

25%

30%

0 10 20 30 40 50 60 70 80 90

% of Vehicles

% of Excess Emissions

Excess HC%

Excess CO%

Excess NOx%

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LEI Clean Screen Selection Criteria 

To maintain flexibility in the selection of LEI vehicles (both quantity and quality), it is suggested that the 

following five criteria be considered. Colorado is proposing using only the HC/CO Fail Rate criteria

however the remaining four will continue to be calculated and if necessary included as part of future LEI 

tables. 

Overall tailpipe fail rate is less than: X% 

HC/CO Fail Rate is less than Y% 

Excess HC is less than: A g/mi 

Excess CO is less than: B g/mi 

Excess NOx is less than C g/mi 

To ignore one or more of the criteria, either a high or a low value is entered. For example, to select all 

vehicle classes with an overall fail rate of less than 1%, entries would be 1%, 99%, 99, 99 and 99.

Average excess emissions per vehicle relate more directly to mass emissions benefits than fail rate. 

Given two groups of vehicles with the same fail rate, one group containing poor fuel economy vehicles 

and one group containing good fuel economy vehicles, the group with the poor fuel economy vehicles

will contribute greater excess emissions. However, using fail rate as the criteria is easier for the media 

and the public to understand.

Hybrid Method Evaluation 

The hybrid method of selecting vehicles for clean screen was evaluated using 2006 data. I/M results of

vehicles that would have been selected using the hybrid method are compared to the results of the 5%

audit sample of vehicles passing the current 2-hit screen and vehicles that were identified as clean (2-

hits) but for unknown reasons did not participate in the current clean screen program.

Table 2 below shows that projected results for vehicles selected using the hybrid method compare

favorably to the current RSD 2-hit method. Both the tailpipe and overall fail rates, which includes

evaporative test failures, are 0.3% lower. The hybrid method was modeled using RSD CO and HC

cutpoints of 0.5% and 200ppm respectively and a simple LEI HC/CO fail rate of 2%. 

Table 2 Clean Screen Method Evaluation Summary

Method Sample 

Number 

of 

Vehicles 

IM240 

Tailpipe 

Fail 

Rate 

Overall I/M 

Fail Rate 

Hybrid Sample 31,644 0.34% 2.6%

2006 RSD 2-hit 5% Audit Sample 1,509 0.46% 2.5%

Other RSD 2-hit Sample Meeting 

Screen Criteria 15,299 0.66% 2.9%

Combined RSD 2-hit Samples 16,808 0.64% 2.9%

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The results show that the effectiveness of the hybrid method is equivalent to that of the current clean

screening method using two RSD measurements. 

Further investigation is being conducted to determine if the evaporative failures can be cost effectively

reduced for both methods by applying an additional restriction on clean screens for models with a

pattern of evaporative test failures. 

The remainder of this section provides details of the hybrid evaluation. 

Hybrid Evaluation Process 

As noted above, the hybrid method of selecting vehicles for clean screen was evaluated using 2006 I/M 

results of vehicles that would have been selected using this method. 

Vehicle owners are notified of their clean screen eligibility one to two months prior to their registration

renewal date. Change of ownership vehicles that are inspected off-cycle are, therefore, not able to take 

advantage of clean screening. Historically, vehicles changing ownership have higher emissions and 

failure rates than other vehicles. To accurately project hybrid clean screen program performance these

off-cycle tests are removed from the evaluation sample. To accomplish this, vehicles tested in 2006

were selected where their first test occurred within 23-25 months of their first test in 2004. This 

identified 303,525 vehicles tested with IM240. 

RSD measurements from the 12-month window in advance of the IM240 test were identified for the 

303,525 vehicles. Of these, 23,521 vehicles had at least two measurements and 48,438 vehicles had

a single measurement. 

Vehicles with two measurements would typically be considered for current 2-hit screening method.

Vehicles that accepted the clean screen option would not typically have an IM240 test in 2006 and,

therefore, are not typically included in the extracted sample of vehicles with two measurements 

described above. The extracted sample of vehicles with two measurements does include the 5% audit 

sample, vehicles that did not pass the screen, vehicles that did not accept the clean screen option and

vehicles for which the second qualifying RSD may not have been in time to be included before the 

processing deadline. 

Vehicles with a single measurement passed the hybrid method if their HC and CO emissions were

below 200ppm and 0.5% respectively on their RSD measurement and their LEI group had an HC/CO

fail rate of less than 2%. Results are compared to both the 5% audit sample and the other RSD 2-hit 

vehicles screened using the current 2-hit method. 

Since vehicles with two qualifying measurements would not be eligible for the hybrid method they were

not considered part of the hybrid evaluation. However, vehicles from this group that would have met 

the 2-hit RSD screen criteria provide another point of reference for comparison with the effectiveness of

the hybrid method. Therefore, results for three samples are considered in the following charts and

tables: 

• 2006 RSD 2-hit Audit sample

• Hybrid Method sample 

• Other RSD 2-hit sample; vehicles with two RSD measurements that met the 2-hit screen

criteria. 

Figure 4 shows that MY distributions of vehicles meeting the screening criteria from the ‘Hybrid Sample’

and the ‘Other 2-Hit Sample’ vehicles are similar to the ‘Audit Sample’ except that the ‘Audit Sample’ 

includes more 2002 models. Most 2002 models were not tested in 2004 and, as a result of the sample

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selection method described above, were not included in the ‘Hybrid Sample’ or the ‘Other 2-hit 

Sample’. Since the 2002 models are the newest full model year, and are expected to be virtually all

clean, their omission does not compromise the hybrid evaluation although the evaluated hybrid

effectiveness may appear to be less good than if all these 2002 models had been included. 

Figure 4 – Vehicle Age Distribution of Clean Screen Vehicles 

Age Distribution of Vehicle Samples Meeting Clean 

Screen Criteria

0%

5%

10%

15%

20%

25%

30%

198219841986198819901992199419961998200020022004

Model Year

% of Candidates

Hybrid

RSD 2-hit

5% Audit

Figure 5 shows the projected hybrid pass rate vs. the current Clean Screen program by model year in 

2006. The pass rate is higher for the newest models but drops rapidly below the current program for 

1996 and older models, which were over ten years old in 2006. The overall hybrid pass rate was 68%

of candidates vs. 78% for current 2-hit RSD. 

Figure 5 – Hybrid vs. Current Clean Screen Program Pass Rate 

Pass R a te of C lean Scre en C andidate s in 200 6 and

Proje cted H yb rid M e thod

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

198219841986198819901992199419961998200020022004

M odel Y ear

% Passing Screen

R SD 2-H it I/M Eligibles

H ybr id

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Tables 3, 4 , 5 and 6 show the IM240 test results for the ‘Audit Sample’, ‘Hybrid Sample’, ‘Other RSD 

2-hit Sample’, and ‘Audit Sample and Other RSD 2-Hit Sample Combined’. The tables show the MY

distribution, the tailpipe fail rate, the overall fail rate and the average IM240 g/mi emissions of vehicles

passing the screens. 

Despite the absence of a full complement of 2002 models, the average emissions of vehicles passing

the Hybrid method are lower than the ‘Audit Sample’ by 0.01, 0.1 and 0.01 g/mi for HC, CO and NOx

respectively. 

The average emissions of vehicles passing the Hybrid method are lower than the ‘Other RSD 2-hit 

Sample’ by 0.05, 0.7 and 0.09 g/mi for HC, CO and NOx respectively. 

The Hybrid method is therefore at least as effective as the RSD 2-hit method. 

Table 3 – Audit Sample 

2006 Audit Sample Vehicles Passing 2-Hit Screen with RSD CO <0.5% and HC <200ppm 

Model

Year 

Fraction

of 

Screen 

Passes

IM240 

Tailpipe

Fail 

Rate

IM 

Overall

Fail 

Rate

Model

Year 

Vehicles IM240 

Tailpipe

Failures

Overall 

Failures

IM240 

Avg. 

HC

g/mi 

IM240 

Avg. 

CO 

g/mi 

IM240 

Avg. 

NOx

g/mi 

1982 0% 0.00% 0.0% 1982 0 0 0 - - -

1983 0% 0.00% 0.0% 1983 0 0 0 - - -

1984 0% 0.00% 0.0% 1984 1 0 0 4.37 21.2 4.20

1985 0% 0.00% 0.0% 1985 1 0 0 0.98 12.9 2.02

1986 0% 0.00% 0.0% 1986 2 0 0 1.92 14.7 2.87

1987 0% 0.00% 0.0% 1987 2 0 0 1.12 8.1 1.72

1988 1% 7.69% 7.7% 1988 13 1 1 1.45 10.7 1.82

1989 1% 0.00% 9.1% 1989 11 0 1 0.93 7.8 2.19

1990 1% 4.76% 9.5% 1990 21 1 2 1.04 12.2 2.00

1991 1% 0.00% 0.0% 1991 15 0 0 0.78 8.8 1.69

1992 2% 0.00% 0.0% 1992 23 0 0 1.04 9.7 2.07

1993 2% 0.00% 2.9% 1993 34 0 1 0.74 7.3 1.47

1994 3% 0.00% 0.0% 1994 50 0 0 0.56 5.8 1.35

1995 4% 1.54% 7.7% 1995 65 1 5 0.62 5.5 1.30

1996 6% 0.00% 2.1% 1996 96 0 2 0.38 4.3 1.28

1997 6% 0.00% 1.0% 1997 98 0 1 0.37 4.1 1.30

1998 12% 0.56% 2.2% 1998 178 1 4 0.29 3.6 1.03

1999 8% 0.84% 2.5% 1999 119 1 3 0.30 3.0 1.02

2000 17% 0.78% 1.9% 2000 258 2 5 0.20 2.8 0.68

2001 10% 0.00% 2.6% 2001 153 0 4 0.12 2.2 0.48

2002 22% 0.00% 2.4% 2002 338 0 8 0.11 1.8 0.47

2003 2% 0.00% 0.0% 2003 31 0 0 0.14 2.6 0.60

2004 0% 0.00% 0.0% 2004 0 0 0 - - -

2005 0% 0.00% 0.0% 2005 0 0 0 - - -

Total 100% 0.46% 2.5% 1,509 7 37 0.31 3.6 0.90

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Table 4 – Hybrid Sample

Projected 2006 Hybrid Screen Passes: RSD CO <0.5% & HC < 200ppm, LEI HC/CO Failure < 2%

Model

Year 

Fraction

of 

Screen 

Passes

IM240 

Tailpipe

Fail 

Rate

IM 

Overall

Fail 

Rate

Model

Year 

Vehicles IM240 

Tailpipe

Failures

Overall 

Failures

IM240 

Avg. 

HC

g/mi 

IM240 

Avg. 

CO 

g/mi 

IM240 

Avg. 

NOx

g/mi 

1982 0% 0.00% 0.0% 1982 1 0 0 4.00 31.8 3.10

1983 0% 0.00% 0.0% 1983 0 0 0 - - -

1984 0% 6.25% 18.8% 1984 16 1 3 1.76 20.7 2.14

1985 0% 0.00% 16.7% 1985 6 0 1 1.43 14.8 1.93

1986 0% 0.00% 0.0% 1986 38 0 0 0.99 11.1 1.92

1987 0% 0.00% 18.2% 1987 11 0 2 0.99 10.2 2.17

1988 0% 0.00% 3.3% 1988 30 0 1 0.95 9.4 1.53

1989 0% 0.00% 3.1% 1989 32 0 1 0.79 8.4 1.68

1990 1% 0.56% 3.3% 1990 180 1 6 0.82 7.8 1.76

1991 1% 0.00% 4.2% 1991 236 0 10 0.76 7.7 1.74

1992 2% 0.16% 2.3% 1992 607 1 14 0.67 7.1 1.53

1993 2% 1.15% 4.3% 1993 697 8 30 0.70 7.3 1.71

1994 3% 0.91% 3.4% 1994 993 9 34 0.56 5.9 1.34

1995 5% 0.84% 3.1% 1995 1,426 12 44 0.51 5.1 1.34

1996 9% 0.46% 3.5% 1996 2,820 13 98 0.38 4.2 1.13

1997 9% 0.51% 3.8% 1997 2,943 15 113 0.36 4.1 1.11

1998 16% 0.29% 2.0% 1998 5,214 15 103 0.30 3.4 0.91

1999 12% 0.21% 2.3% 1999 3,781 8 87 0.27 3.0 0.86

2000 24% 0.23% 2.3% 2000 7,538 17 170 0.20 2.5 0.66

2001 8% 0.17% 2.2% 2001 2,387 4 52 0.14 2.1 0.48

2002 5% 0.25% 2.3% 2002 1,601 4 37 0.12 2.0 0.44

2003 2% 0.00% 1.2% 2003 753 0 9 0.09 1.7 0.36

2004 1% 0.00% 1.2% 2004 326 0 4 0.08 1.5 0.29

2005 0% 0.00% 0.0% 2005 8 0 0 0.07 1.3 0.28

Total 100% 0.34% 2.6% 31,644 108 819 0.30 3.5 0.89

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Table 5 – Other RSD 2-Hit Sample 

Other Vehicles Passing 2-hit Screen with CO <0.5% and HC <200ppm 

Model

Year 

Fraction

of 

Screen 

Passes

IM240 

Tailpipe

Fail 

Rate

IM 

Overall

Fail 

Rate

Model

Year 

Vehicles IM240 

Tailpipe

Failures

Overall 

Failures

IM240 

Avg. 

HC

g/mi 

IM240 

Avg. 

CO 

g/mi 

IM240 

Avg. 

NOx

g/mi 

1982 0% 0.00% 0.0% 1982 4 0 0 1.96 15.6 3.15

1983 0% 0.00% 0.0% 1983 2 0 0 1.58 11.5 4.15

1984 0% 0.00% 7.1% 1984 14 0 1 1.88 21.2 2.46

1985 0% 4.35% 4.3% 1985 23 1 1 1.15 14.1 2.33

1986 0% 2.22% 4.4% 1986 45 1 2 1.30 13.9 2.28

1987 0% 5.45% 9.1% 1987 55 3 5 1.13 11.9 2.33

1988 1% 1.71% 4.3% 1988 117 2 5 1.13 11.9 1.95

1989 1% 2.70% 5.4% 1989 111 3 6 1.04 11.6 1.94

1990 2% 0.87% 6.1% 1990 230 2 14 0.89 8.7 1.79

1991 2% 1.96% 7.5% 1991 255 5 19 0.84 8.8 1.83

1992 3% 3.42% 7.8% 1992 409 14 32 0.82 9.4 1.72

1993 3% 1.61% 4.6% 1993 436 7 20 0.73 7.9 1.86

1994 4% 1.53% 4.1% 1994 589 9 24 0.70 7.4 1.59

1995 5% 2.08% 5.6% 1995 818 17 46 0.63 6.2 1.45

1996 8% 0.51% 2.1% 1996 1,167 6 25 0.41 4.7 1.26

1997 8% 0.89% 3.7% 1997 1,237 11 46 0.40 4.4 1.17

1998 13% 0.63% 2.3% 1998 2,054 13 48 0.31 3.9 0.97

1999 10% 0.06% 2.0% 1999 1,578 1 32 0.27 3.2 0.88

2000 20% 0.20% 2.2% 2000 3,037 6 67 0.20 2.7 0.66

2001 7% 0.00% 2.3% 2001 1,142 0 26 0.13 2.2 0.50

2002 5% 0.00% 1.6% 2002 770 0 12 0.11 1.8 0.43

2003 5% 0.00% 1.3% 2003 775 0 10 0.09 1.6 0.36

2004 3% 0.00% 0.5% 2004 420 0 2 0.08 1.5 0.29

2005 0% 0.00% 0.0% 2005 11 0 0 0.07 1.6 0.19

Total 100% 0.66% 2.9% 15,299 101 443 0.35 4.2 0.98

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Table 6 - Audit Sample and Other RSD 2-Hit Sample Combined 

2006 Audit Sample + Other 2-Hit Passing 2-Hit Screen with RSD CO <0.5% and HC <220ppm

Model

Year 

Fraction

of 

Screen 

Passes

IM240 

Tailpipe

Fail 

Rate

IM 

Overall

Fail 

Rate

Model

Year 

Vehicles IM240 

Tailpipe

Failures

Overall 

Failures

IM240 

Avg. 

HC

g/mi 

IM240 

Avg. 

CO 

g/mi 

IM240 

Avg. 

NOx

g/mi 

1982 0% 1982 4 - - 1.96 15.61 3.15

1983 0% 1983 2 - - 1.58 11.53 4.15

1984 0% 0.00% 6.7% 1984 15 - 1 2.05 21.23 2.58

1985 0% 4.17% 4.2% 1985 24 1 1 1.15 14.04 2.31

1986 0% 2.13% 4.3% 1986 47 1 2 1.33 13.96 2.30

1987 0% 5.26% 8.8% 1987 57 3 5 1.13 11.77 2.31

1988 1% 2.31% 4.6% 1988 130 3 6 1.17 11.80 1.94

1989 1% 2.46% 5.7% 1989 122 3 7 1.03 11.27 1.96

1990 1% 1.20% 6.4% 1990 251 3 16 0.91 9.00 1.81

1991 1% 1.85% 7.0% 1991 270 5 19 0.84 8.83 1.82

1992 3% 3.24% 7.4% 1992 432 14 32 0.84 9.43 1.74

1993 3% 1.49% 4.5% 1993 470 7 21 0.73 7.89 1.83

1994 4% 1.41% 3.8% 1994 639 9 24 0.69 7.28 1.57

1995 5% 2.04% 5.8% 1995 883 18 51 0.63 6.19 1.44

1996 8% 0.48% 2.1% 1996 1,263 6 27 0.41 4.71 1.27

1997 8% 0.82% 3.5% 1997 1,335 11 47 0.39 4.40 1.18

1998 13% 0.63% 2.3% 1998 2,232 14 52 0.31 3.86 0.97

1999 10% 0.12% 2.1% 1999 1,697 2 35 0.27 3.16 0.89

2000 20% 0.24% 2.2% 2000 3,295 8 72 0.20 2.69 0.67

2001 8% 0.00% 2.3% 2001 1,295 - 30 0.13 2.15 0.50

2002 7% 0.00% 1.8% 2002 1,108 - 20 0.11 1.82 0.44

2003 5% 0.00% 1.2% 2003 806 - 10 0.09 1.67 0.37

2004 2% 2004 420 - 2 0.08 1.51 0.29

2005 0% 2005 11 - - 0.07 1.58 0.19

Total 100% 0.64% 2.9% 16,808 108 480 0.35 4.1 0.97

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