These documents, sometimes referred to as Private Letter Rulings, are taken from the IRS Written Determinations page; the IRS also publishes a fuller explanation of what they are and what they mean. The collection is updated (at our end) daily.
Ethiopia's population was estimated at 51.7 million in 1990. According to the nation's only census, conducted in 1984, Ethiopia's population was about 42 million. But the census was far from comprehensive.
The current population of Costa Rica is approximately 4.95 million, up from the 4.58 million at the 2011 census. This makes Costa Rica the 120th most populous country in the world. Of course, this number does not factor in the nearly 2.2 million visitors that Costa Rica receives per year!