The evaluation metric for this competition is MAPE
. The MAPE is a measure of prediction accuracy, where the forecast error is measured relative to the magnitude of the quantity of interest.  MAPE can be expressed as:
\[ MAPE = \frac{1}{n} \sum_{i=1}^n (\frac{\left|A_{t}-F_{t}\right|}{A_{t}})  \]
where At is the actual value and Ft is the forecast value.