A blog by Rob J Hyndman 

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Forecasting the recession

Published on 18 August 2009

Fore­cast­ers are under the pump with a reces­sion that many didn’t see com­ing. As I don’t do any macro­eco­nomic fore­cast­ing, I can sit back and smile smugly at some of my col­leagues while I work on sim­pler prob­lems such as fore­cast­ing in epi­demi­ol­ogy, demog­ra­phy and energy demand.

Some of those col­leagues are cited in the Wall Street Jour­nal today. The fol­low­ing quo­ta­tion is inter­est­ing:

The spate of cloudy crys­tal balls high­lighted an uncom­fort­able real­ity about telling the future: It is hard­est when it is most important.

Ini­tially it sounds profound—just when you need to fore­cast, the data con­spires against you and makes it dif­fi­cult. But in hind­sight I don’t think it is like that at all.

When it is easy to fore­cast (e.g., when there is a steady increas­ing trend and lit­tle volatil­ity), no-​​one is think­ing about the fore­cast­ing because it is obvi­ous what is going to hap­pen. And so fore­cast­ing doesn’t seem impor­tant because it doesn’t get much atten­tion. But when there is a lot of volatil­ity, then peo­ple look to fore­cast­ing for answers, just when it is hard to do it accu­rately. Con­se­quently, it is hard­est when peo­ple are think­ing about it, because they only think about it when it is hard.

That said, macro­eco­nomic fore­cast­ing has a bad name for a good rea­son. Far too many con­fi­dent fore­casts are made with­out dis­cus­sion of the uncer­tainty. If only every fore­caster pro­duced pre­dic­tion inter­vals every time they made a fore­cast, the users would realise that macro­eco­nomic fore­casts are lit­tle bet­ter than shoot­ing blindfolded.

See my talk on Fore­cast­ing and the impor­tance of being uncer­tain where I argue for manda­tory pre­dic­tion inter­vals for every point fore­cast.


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4 Comments  comments 
  • Víc­tor M. García-​​Guerrero

    Hi Rob!!! I agree with you about this point. But, many times deci­sion mak­ers or politi­cians need exact data. I mean, for exam­ple, many times polit­i­cans ask to demog­ra­phers for the future pop­u­la­tion fig­ures with the aim to allo­cate bud­gets. If demog­ra­phers give them an inter­val, how they could deter­mi­nate how much money goes, for exam­ple, to edu­ca­tion, to which regions, etc. Another exam­ple is the cal­cu­la­tion of GNP per capita, how would politi­cians use pop­u­la­tion pre­dic­tion inter­vals to deter­mi­nate the near future income. What do you think about it?

    I really admire your work on forecasting.

    From the other side of the world. Greetings.

    Víc­tor M. García-​​Guerrero

    • http://www.robjhyndman.com Rob J Hyndman

      Hi Vic­tor. In the exam­ples you give, the uncer­tainty in the demo­graphic input fore­casts needs to be taken into account in deter­min­ing the eco­nomic out­put fore­casts. But there may also be uncer­tainty in the esti­mated rela­tion­ship and in other inputs. In such cases, you need to use either the­ory or sim­u­la­tion to deter­mine the final level of uncer­tainty in the eco­nomic out­puts. So the demog­ra­phers may need to pro­vide a pre­dic­tion dis­tri­b­u­tion rather than just an inter­val to allow the final uncer­tainty to be estimated.

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  • http://www.rmit.edu.au/staff/ashton_de_silva Ash­ton de Silva