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From |
adiallo5@worldbank.org |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: RE: Simulation question |

Date |
Thu, 3 Feb 2005 09:22:19 -0500 |

Dear Marteen, Thanks for the answer. My question is precisely how to program Stata to find the best combination of increases in POP and INVEST. I have in mind the case where a lot of dependent variables are involved. I was going around by doing it mechanically (i.e. raising one by one my independent variables to approach the desired result, but it's somewhat painful). I think it's a matrice solving constraint equation. But as I said, I do not know how to do this in Stata. Amadou. "Maarten Buis" <M.Buis@fsw.vu.nl> To: <statalist@hsphsun2.harvard.edu> Sent by: cc: owner-statalist@hsphsun2. Subject: st: RE: Simulation question harvard.edu 02/03/2005 09:00 AM Please respond to statalist Dear Amadou, The easiest answer is that you do not need a simulation. The parameter of POP tells you how much GDP will increase as a result of an unit increase in population. So if the parameter of POP is .5 and GDP is 10, than an increase of 10 (doubling GDP) is achieved by and increase in the population of 20. You could of course find a lot (infinite, actually) of combinations of increases in POP and INVEST that will lead to a 10 point increase in GDP. So you will have to make additional assumptions to narrow that down. Beware of the assumed direction of causality: your model assumes that GDP is caused by POP and INVEST, so doubling GDP causes nothing, but is caused by POP and INVEST. Hope this helps, Maarten -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of adiallo5@worldbank.org Sent: donderdag 3 februari 2005 14:32 To: statalist@hsphsun2.harvard.edu Subject: st: Simulation question Hi, I have a simulation problem. Usually, what I've seen done in simulations is to change values in independent variables and see their result on the (predicted dependent variable). Ex: reg GDP pop invest predict gdphat su gdphat replace pop =pop * 1.03 /* 3% growth of population*/ predict gdphat2 su gdphat2 g diff = gdphat - gdphat2 /*Measure of the impact of the population growth */ Now, here is my question: Suppose I want to double my GDP ? I am interested in how my independent variables will change (in their coeffcients and/or in their observations ???) to meet the new values of GDP. I guess I am facing a constraint problem but do not know how to do this in Stata. How can I do that? Best regards. Amadou. * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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