A number of federal laws require plain language such as the Truth in Lending Act, the Civil Rights Act of 1964, and the Electronic Funds Transfer Act. In June 1998, President Clinton directed all federal agencies to issue all documents and regulations in plain language.

Beginning in 1975, a number of states passed plain-language laws covering such common documents as bank loans, insurance policies, rental agreements, and property-purchase contracts. These laws often state that if a written communication fails the readability requirement, the offended party may sue and collect damages. Such failures have resulted in court judgments.

States such as California also require plain language in all agency documents, including "any contract, form, license, announcement, regulation, manual, memorandum, or any other written communication that is necessary to carry out the agency's responsibilities under the law" (Section 6215 of the California Government Code). California defines plain language as "written or displayed so that the meaning of regulations will be easily understood by those persons directly affected by them" (Section 11349 of the Administrative Code).

Textbook publishers After 80 years, textbook publishers consider the grade level of textbooks as more important than cost, the choice of personnel, or the physical features of books. All of them use word-frequency lists. Eighty-nine percent of them use readability formulas in evaluating the grade-levels of texts, along with other methods of testing. Widely read children's publications such as My Weekly Reader and magazines published by National Geographic for children of different ages have used the formulas along with field-testing and other methods (Chall and Conard 1991).

Using the formulas

Formula discrepancies The discrepancy between the scores of different formulas has long been perplexing. For example, the scores for the following four paragraphs are:

Critics have often cited such discrepancies as indications of the lack of precision of the formulas. Kern (1979) argued that the discrepancies among the Kincaid and Caylor formulas deprive them of usefulness, and that the military should discard them. What Kern ignores in his review are the correlations of the formulas with comprehension tests. What is important is not how the formulas agree or disagree on a particular text, but their degree of consistency in predicting difficulty over a range of graded texts.

The most obvious causes of the discrepancies are the different variables used by different formulas and the different criterion scores used in their development. The formulas - like reading tests - simply do not have a common zero point (Klare 1982). The criterion score is the required level of comprehension indicating reading success as indicated by the percentage of correct answers on a reading test. For example, a formula can predict the level of reading skill required to answer correctly 75 % of the questions on a reading test based on a criterion passage.

The FORCAST formula uses a 50% criterion score as measured by multiple-choice tests. The Flesch and Dale-Chall formulas use a 75% score, Gunning Fog formula, a 90% score, and the McLaughlin SMOG formula a 100% score. The formulas developed with the higher criterion scores tend to predict higher scores, while those the highest validity correlations (e.g., Dale-Chall and Flesch) tend to predict lower scores.