The last equation, albeit true, needs clarification for better understanding by ordinary users: it is not immediately self-evident how the author, deriving the equation, 'got rid off' the activities, substituting instead directly the activity coefficients. Mathematically it is true, but it should be shown in a bit more depth in my opinion.
There is no regular TV broadcasted "Have You Say" on the BBC World
editIt is very sad that the Wiki article fails to introduce clarity (and thereby generates critical clarity) about the status and the change that happened to the TV broadcasted World Have Your Say (WHYS). Now and since around 2011 the WHYS hasn't been a regular schedule TV program on BBC World - a fact absolutely tectonic and essential for any reader and user of WHYS as well as any one trying to study the activity and tendencies of the BBC corporation. Not the BBC says that it is "on an adhoc basis" (see https://worldhaveyoursay.wordpress.com/whys-faqs/) which means it is almost never on BBC World TV and even at rare times when it is, its interviewed audience nowadays is selected by the BBC according to some "closed" and non-transparent considerations of the BBC itself. The regular broadcasting of WHYS on TV on BBC World was done for years in the past and this format had a special influence and strength because of the scale of the international TV audience of the BBCWorld TV). The selection of the interviewed people was done according to the natural rankings defined by the votes on the blog by the world public itself. This program in the shape and form we knew it, with its influence and clear transparent democratic format of its platform for population's opinions, totally ceased to exist in around 2011! None of the above continues to exist today in terms of WHYS of the scale and regularity and frequency on TV on the BBCWorld. The Wikipedia article completely fails to clarify and describe this change and the situation, which is of essence, and the omission of which predictably may create a distorted understanding of the history of dynamics, philosophy and influence (and even ethics) of the Have Your Say initiative.