"Prediction is difficult, especially about the future"

[Benjamin Zimmer]

Speaking of incongruous quotations about the future, the databases have
dozens of cites since at least 1980 for "Prediction is difficult,
especially about the future" (or some variation thereof).  Attribution is
awarded to the usual suspects, from Mark Twain to Yogi Berra to an
anonymous Chinese proverb-maker, but the physicist Niels Bohr usually gets
the credit.  It also gets attributed to Bohr's Danish compatriots, Piet
Hein and Robert Storm Petersen.  This post from Ole Nielsby on
soc.culture.nordic looks authoritative:

http://groups-beta.google.com/group/soc.culture.nordic/msg/864c4d82e5d91bff

        Aron Felix Gurski <agur... at sn.no> wrote:
        >Jon Haugsand wrote:
        >>
        >> Who said "Prediction is difficult, especially of the future"?
        >> (Or "Det er vanskelig at spaa, isaer om fremtiden".)
        >I don't know, but it *should* have been Piet Hein.

        The "Bevingede ord" ("Winged Words") dictionary of quotations
        (5th ed., GAD, 1979) says:

        ENGLISH: (xl by me)

        "Prediction is difficult - especially of the future" - is of
        unknown origin and certainly not by Storm Petersen, to whom it
        is always accredited. The phrase possibly occurred as a pun in
        the danish parlament 1935-39; it is quoted as such in the 4th
        book of memoirs by K.K. Steincke [social democrat MP and
        minister], *Goodbye and thanks*, p227; 1948, which covers
        aforementioned period of time. The originator was queried in
        public, but nobody seemed to know him. - On inquiry, Steincke
        (1880-1963) stated that he did not remember who it was.

        DANISH:
        "Det er svært at spå - især om fremtiden" - er af ukendt
        oprindelse og i hvert fald ikke af Storm Petersen, som altid
        får skyld for sætningen. Den er muligvis forefaldet som en
        sprogblomst i Folketinget 1935-39, gengives i hvert fald som
        sådan i K.K. Steincke's fjerde erindringsbog *Farvel og tak*,
        227; 1948, som omfatter nævnte tidsrum. Ophavsmanden har
        været offentligt efterlyst, men ingen synes at kende ham. -
        Steincke (1880-1963) har på forespørgsel oplyst, at han ikke
        huskede hvem det var.


-- Ben Zimmer