July 1, 2004

Potential Windshield Replacement Study Methodology

The auto glass industry has struggled to achieve an accurate estimate of how many windshields are replaced in the United State every year. One reason is that most researchers approach the question from a strictly quantitative or numerical starting point. In other words, an answer is sought by trying to determine how many windshields are manufactured for the replacement market in a given year. This approach has proven impractical for a number of reasons including:

1.) Most manufacturer production figures are not publicly available;
2.) All manufacturers do not report production figures even to the private informational clearinghouse(s) that exist;
3.) Imported windshields are not included;
4.) All windshields produced for replacement are not always used for replacement purposes;
5.) Some windshields produced for replacement purposes in a given year remain in inventory at the end of the year.

Additional challenges include:

1.) AGR has traditionally attracted casual, part-time operators that keep no installation records and, even if they did, no entity exists to compile those records;
2.) Except in Connecticut, AGR practitioners are not licensed so there is no accurate national data base to determine how many AGR companies there are or how many windshields they install;
3.) Consumers do not repair or replace all damaged windshields that qualify for repair or replacement.

Mr. David Bedwell, an AGR consultant to the National Glass Association, has studied the auto glass industry for 35 years. He determined the most accurate way to quantify the number of replaced windshields was to begin with a reliable control group and, from that control group, determine an average windshield breakage percentage for each U.S. state.

Once the breakage percentage was established for each state, the number of windshields replaced during a given period could be more accurately estimated by multiplying the breakage percentage by the total vehicle population of each state. Figures for the total vehicle population of each state are available from a number of government and private sources.

In order to derive the breakage percentage, Mr. Bedwell was provided with auto glass claims reports by a national insurance company. These reports listed the total windshields replaced by the company during a given period. Because the number of policyholders and the percentage of auto insurance controlled by the insurance company were known by the researcher, he was able to extrapolate a windshield replacement percentage for the insurance control group. It was assumed that all insurance companies would have similar breakage rates since their policyholders drove under the same conditions as the control group.

Once the breakage percentage was determined for each state, it was then applied to the total state vehicle population, and subsequently to the county vehicle population, to achieve an estimated number of windshields replaced during the year.

When the totals of the 50 states were complete, the results were compared to the gross national windshield replacement figures of several other studies either purchased by or available to the researcher. All three studies were within 45,000 windshield units of one another nationally.

The NGA's study was further refined by using the American Map Corporation's book entitled "Pinstripe Control Atlas". This reference guide allowed the researcher to provide maps that identify counties and the government's Major Metropolitan Service Areas (MMSA).

The NGA study does have one weakness that we readily acknowledge. The insurance control group cannot count the number of damaged windshields in need of replacement that were not replaced because they were never reported to the insurance company.

One such factor would be states that allow or insurance customers that opt for high insurance deductibles. In such cases, the insured may not file a claim knowing the replacement cost falls within his deductible. Similarly, some policy-holders may be reluctant to file claims unless the damage is "major", or, they perceive increased premium rates or policy cancellation may occur if a claim is filed.

At this writing, the NGA does not know exactly how pervasive such consumer perceptions are. In an effort to correct this shortcoming, the NGA's Coalition for Auto Glass Safety & Public Awareness has commissioned a series of consumer focus groups to be conducted during the summer of 2004. These focus groups will seek to identify consumer attitudes toward auto glass replacement and, if possible, to determine what percentage ignore auto glass damage for fear of their insurance carrier's reaction. The NGA will publish the results of its focus groups to its members as soon as possible.

Leo M. Cyr, Vice President
NGA Auto Glass Division