Although the rules of English grammar remain constant throughout the world, there are some differences among expressions and words used in various English-speaking countries. However, almost 300 million North Americans work and live in English. Consequently, North America represents the single largest block of English-speaking peoples in the world. In addition, North America has the world's largest economy. As a result, it only makes sense to use a North American proofreading-editing service to assist you in your written English, particularly for business or technical subjects.