Why aren't there numbers in parentheses after some data items in the lists?
In creating the lists that appear in this web site, I made a reasonable effort to find the number associated with each item in the lists, either from an expert source, by calculation based on known quantities, or by estimation. Obviously, some things are very difficult to calculate or even to estimate with any degree of precision. The best that can be said for them is that their numbers fall somewhere within some large category, such as millions or trillions.
In such cases, the item is placed on the page which appears to be a reasonable estimate of their value. The absence of a value in parentheses implies that the best that can be said for the item is that its value falls somewhere between 1 and 999 times the number in the caption on the top of the page.