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When news on the radio says that a given investment instrument’s price is up or down by some stated percentage or monetary amount, but it doesn’t say what that’s compared to, is there a convention defining this? For example, do they mean a year ago, a day ago, a minute ago, since the last opening or closing, or since some event that is in the news about that instrument, such as a board choosing a new company president? This happens often on Bloomberg radio, but I visited their website and couldn’t find any page that explained this.
Per Claude AI:
For reports during trading hours or end-of-day summaries, the default comparison is typically to the previous trading day’s closing price.
For after-hours or pre-market reports, the reference point is still usually the most recent regular trading session’s close, although sometimes they may specify “after-hours” gains/losses separately.
Important exceptions:
When major news events occur (earnings announcements, Fed decisions, etc.), reporters sometimes specify “since the announcement” or give intraday comparisonsWeekly/monthly market summaries will usually specify the timeframe explicitly.
Breaking news about significant moves may reference the timeframe that makes the story most relevant.
The key is that financial media assumes their audience understands this daily comparison convention. When they mean something different (like year-over-year changes or intraday moves), they typically state it explicitly to avoid confusion.
I hope that helps.
Good question…