That is one way, the other way is that the person who has an interview, tells people close to him and they pass on the info. Not seen anyone mention Chris Powell yet and his odds are coming down.
Also if you look at the betting Sherwood and Clarke's odds have not really gone out much and they remain favourites, which would infer they have been interviewed.
Clement and Garde odds have drifted, because they have distanced themselves from the job.
Bookies are more often right, and our manager will be one of the front runners at the bookies. We will know through the bookies before an announcement is made, as there will be a late flurry of bets on one person as word leaks out.