Here's a short story:

The "Billboard" 200 is a record chart ranking the 200 most popular music albums and EPs in the United States. It is published weekly by "Billboard" magazine. It is frequently used to convey the popularity of an artist or groups of artists. Often, a recording act will be remembered by its "number ones", those of their albums that outperformed all others during at least one week. 

The chart is based mostly on sales (both at retail and digital) of albums in the United States. The weekly sales period was originally Monday to Sunday when Nielsen started tracking sales in 1991, but since July 2015, tracking week begins on Friday (to coincide with the Global Release Date of the music industry) and ends on Thursday. A new chart is published the following Tuesday with an issue post-dated to the Saturday of the following week. The chart's streaming schedule is also tracked from Friday to Thursday. 

New product is released to the American market on Fridays. Digital downloads of albums are also included in "Billboard" 200 tabulation. Albums that are not licensed for retail sale in the United States (yet purchased in the U.S. as imports) are not eligible to chart. A long-standing policy which made titles that are sold exclusively by specific retail outlets (such as Walmart and Starbucks) ineligible for charting, was reversed on November 7, 2007, and took effect in the issue dated November 17. (End of story)

Provide your best guess for the following question. Give ONLY the guess, no other words or explanation.

For example:

Guess: <most likely guess, as short as possible; not a complete sentence, just the guess!>

Here are a few examples of questions and answers:

Question: what is the chart based on?
Guess: the 200 most popular music albums and EPs

Question: what is a recording act remembered by?
Guess: by its "number ones"

Question: how often is it published?
Guess: weekly

Question: on what day?
Guess: Saturday

Question: are all albums included in the chart?
Guess: no

Question: which are not?
Guess: Albums that are not licensed for retail sale in the United States

Question: can these be bought in the US anyways?
Guess: yes

Question: What did Nielsen start keeping track of?
Guess: sales

Question: when did he start?
Guess: in 1991

Question: what days were they between?
Guess: originally Monday to Sunday

Question: when did this change?
Guess: July 2015

Question: to what?
Guess: Friday to Thursday.

Question: what happened to titles sold by retail outlets in the past?
Guess: it was reversed

Question: what happened before it was reversed?
Guess: they were ineligible for charting,

Question: when was it reversed?
Guess: November 7, 2007

Question: what is Billboard 200?
Guess: a record chart

Question: what is it used to convey?
Guess: the 200 most popular music albums and EPs in the United States

Now answer the following question in the same format.

Question: is it worldwide?

no