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Market Integration in Mozambique - International Food Policy ...

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If we have sufficient observations, we can use non-parametric smooth<strong>in</strong>g methods to get a sense of the evolution of the<br />

transaction costs. We can estimate the model on the first 1:N observations and note down the estimated transaction cost for<br />

this sub-sample. We can then estimate the model aga<strong>in</strong> on the 2:N+1 observations and aga<strong>in</strong> write down the estimated<br />

transaction cost. This can go on until we arrive at the end of our price series T-N:T. This will result <strong>in</strong> a smoothed l<strong>in</strong>e for the<br />

SUMMARY | APRIL 2010<br />

transaction cost TC. In pr<strong>in</strong>ciple, we can smooth both the adjustment parameter and the transaction cost <strong>in</strong> this way. However,<br />

<strong>in</strong> this paper, we are <strong>in</strong>terested <strong>in</strong> mak<strong>in</strong>g the transaction cost estimate more flexible and so we will estimate only one<br />

constant adjustment speed.<br />

In particular, we will start by estimat<strong>in</strong>g a simple TAR model as described above. This will lead us to an estimate of the<br />

adjustment speed (ρ) if the price difference is outside the band 6 . Based on this <strong>in</strong>itial estimate for the adjustment speed, we<br />

will estimate a different TC for each t. We do this by choos<strong>in</strong>g a bandwidth h and then, us<strong>in</strong>g a grid search, f<strong>in</strong>d<strong>in</strong>g the TC<br />

such that:

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