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I am testing the cointegration between these variables:

Gold Price (Ringgit),
Exchange Rate - MYR to USD (Ringgit),
Real Effective FX Rate Based on CPI,
T-Bill 10 Years Rate,
Consumer Price Index.

Which variables should I take logarithms of before running the tests?

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  • $\begingroup$ Gold Price (Ringgit), Exchange Rate - MYR to USD (Ringgit), Real Effective FX Rate Based on CPI, T-Bill 10 Years Rate, & Consumer Price Index $\endgroup$ Commented Dec 17, 2015 at 7:00

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In general, Exchange rate is logged, CPI is logged, Gold Price is logged. Interest rates are left like this.

I would suggest, however, to apply the following transformations, because people usually use those: CPI becomes inflation and exchange rate becomes a ap-/depreciation rate.

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  • $\begingroup$ So why not we log for interest rate? And then i am actually taking all the data in differenced form for all the tests (stationary, johansson & engel granger, var). Is it the correct way? $\endgroup$ Commented Dec 17, 2015 at 16:01
  • $\begingroup$ Because it makes no sense to log an interest rate. How would you interpret it ? You take the log of a series because you suspect an underlying exponential form. This is not the case for interest rates. $\endgroup$ Commented Dec 18, 2015 at 9:00
  • $\begingroup$ I have another question. Say for differenced formation. Do i do the first difference for all variables or it depends on the nature of data. For eg. consumer price index? $\endgroup$ Commented Dec 18, 2015 at 9:03
  • $\begingroup$ Your aim is to have stationary variables when estimating. Thus, those which are stationary should not be differenced. $\endgroup$ Commented Dec 18, 2015 at 9:06
  • $\begingroup$ So we should just go for stationarity test first before deciding on the differencing formation? $\endgroup$ Commented Dec 18, 2015 at 9:11

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