Friday, May 28, 2010

Basis points - an admonition

Quite why I am telling people things that any decent financial journalists' stylebook ought to have I don't know, but I have seen so much grievious abuse of the humble basis point over the last month or so ...

1) A basis point is a measure of differences between two interest rates (that's what a "basis" is; also futures and forward rates but those are basically the same thing). It is not merely a posh-sounding way of saying a hundredth of a per cent. Talking about unemployment rates, GDP growth or whatever in basis points doesn't make you look cool, it makes you look like you don't know what you are talking about (I once saw someone write that the rate of income tax was 4000 basis points. Puke.) There is a partial and occasional exception for inflation rates, as of course the inflation rate is the basis between an indexed gilt and an ordinary gilt, but usually it is not correct to talk about inflation in bp either.

2) A basis point is a measure of differences between interest rates. The current 3m dollar LIBOR is 0.54%, it's not 54bp.

3) Given that the basis point has been invented, use it. If one interest rate is 0.6% and another is 0.48%, the spread between them is 12bp. It is not "a 25% difference".

It's not difficult. The phrase "basis points" really just means "and now, since I am talking about interest rates, I am warning you that I propose to talk about adding and subtracting them rather than multiplying and compounding them, and also I am multiplying the quantities by 100 to make them easier to deal with". Bloomberg, Reuters, the FT and WSJ are all regular offenders with respect to this poor little unit.

11 comments:

  1. I once saw someone write that the rate of income tax was 4000 basis points

    The rate?

    ReplyDelete
  2. here is the Bloomberg Style Guide:

    Equivalent to 0.01 percentage point. Use to describe yield, not price: The bond yields 50 basis points more than the benchmark 10-year Treasury note. Use numerals in all cases. Define in stories.

    could use some tightening up.

    ReplyDelete
  3. It was specifically a Bloomberg story that set me off on this one today, and which made mistake number 3.

    ReplyDelete
  4. So far as I know, you are right, correct use of nomenclature is important for clarity, and all that, but ...

    I had a good chuckle as I got to the bottom of this post, only to see the title of the previous one immediately below it. A bit more self-awareness would allow you to avoid others' cheap shots at your expense.

    ReplyDelete
  5. A consistent pseudonym would save you the inconvenience of writing comments only to see them deleted.

    ReplyDelete
  6. Writing and maintaining a stylebook is effort that doesn't count towards this nanosecond's deadline or this month's financial target, so for many, many people, it's easier to not have a stylebook and complain bitterly when writers produce things that aren't in the stylebook-in-the-boss's-head.

    ReplyDelete
  7. Ha, I've just received the note that dd was writing, which contains this complaint up front.

    ReplyDelete
  8. Um, no ... 'basis point' derives from those antediluvian times when price-yield was looked up and interpolated on printed tables (and when 'volatility' was used as synonym for dP/dY), so the primary usage was for change in interest rate in one instrument (providing the 'basis' for the corresponding price change).

    ReplyDelete
  9. WRT 3, to be fair there can be a virtue in reporting both the absolute (bp) and the percentage difference between two interest rates, especially if, as nnyhav points out, it is used to describe a change in a single interest rate. The change in an official interest rate from 0.25% to 1.25% is clearly more significant than a change from 49% to 50%.

    Also, falling in with the general air of pedantry, a bp is a hundredth of a percentage point (WRT to interest rates), not a hundredth of a per cent.

    ReplyDelete
  10. Casino Review for 2021 - FilmfileEurope.com
    Read 토토사이트 시스템배팅 샤오미 our Casino 사설 토토 소액 기준 큐어 벳 Review 2021! 토토 라이브스코어 Find the best reviews, 리드 벳 exclusive signup bonus codes, and start winning 스포츠 토토 중계 넷마블 real money. Claim your welcome bonus.

    ReplyDelete