def mean_percentage_error(y_true, y_pred):
    """Compute the mean percentage error (MPE).

    Parameters
    ----------
    y_true : array-like, shape (n_samples,)
        Ground truth (correct) target values.

    y_pred : array-like, shape (n_samples,)
        Estimated target values.

    Returns
    -------
    mpe : float
    """
    return ((y_true - y_pred) / y_true).mean()