College instructors who adopt this book are (we hope!) twice as likely to continue to use the book the following year as they are to drop it, whereas nonusers are four times as likely to remain...

College instructors who adopt this book are (we hope!) twice as likely to continue to use the book the following year as they are to drop it, whereas nonusers are four times as likely to remain nonusers the following year as they are to adopt this book

In the long term, what proportion of college instructors will be users of this book?