OK, I guess it comes down to a matter of semantic interpretation. Could definitely confuse some bettors, though, IMO.
Thank you both for your insights. I
I found the article (by searching for your quote) and found that they later say (referring to another source), "Among bettors using BetDSI, Trump is now an
overwhelming favorite to be impeached before 2021.
The odds are 1/5 or -500. That means a bettor would have to risk $500 just to win $100 on a bet that Trump will be impeached." Clearly this is referring to what I would call odds of 1:5
against. I'd never heard of expressing odds as "-500", but I find both forms explained here:
https://www.gamblingsites.org/sports-betting/beginners-guide/odds/ . Clearly betting uses different terminology than mathematicians. Some quotes:
"Moneyline odds are also known as American odds, and this is the format most commonly used in the United States. They can be displayed as either a positive or a negative number. A positive number expresses how much a correct wager of $100 would win, while a negative number expresses how much you would need to stake in order to win $100. If you saw odds of +150, you would know that a $100 bet could return $150 in winnings, plus the initial stake of $100. If you saw -150, you would know you need to stake $150 to return $100 in winnings, plus the initial stake of $150. An even money wager (where you stand to win an amount equal to your stake) is expressed as +100."
"Decimal odds used to be associated mostly with mainland Europe, Canada, and Australia. However, they have now largely become the standard at most online bookmakers with the exception of some US betting sites. This is because they are the most straightforward of the three formats and are expressed simply as a single positive number, typically to two decimal places. The number shows how much the total payout will be, including the original stake per unit staked. For example, a winning bet at 1.5 would return a total of $1.50 for every $1 staked. A winning bet at 2.25 would return a total of $2.25 for every $1 staked. An even money bet is expressed as 2.00."
"Fractional odds ... are displayed as a fraction. A simple example is 3/1, which is said as "three to one". 5/1 is said as "five to one", and so on. With 3/1, you can win three units for every one unit staked, and with 5/1 you can win five units for every one unit staked. 1/1 is even money, so you can win one unit for every unit staked." They use the word "against" only in some circumstances, but the order of the numbers as written is always against:for, as I would express it.
Maybe some of you who deal with actual betting will have more to say about this language.