def attenuation(og, fg):
    """Attenuation

    Parameters
    ----------
    og : float
        Original gravity, like 1.053
    fg : float
        Final gravity, like 1.004

    Returns
    -------
    attenuation : float
       Attenuation, like 0.92.

    """
    return (og - fg) / (og - 1.0)