def ts_extend_helper(df):
    """Extend timeseries of length one with a zero measurement in 2020 for plotting purposes"""

    df_out = df

    if df.shape[0] == 1:
        df_out.loc[len(df_out), :] = 0
        df_out.loc[len(df_out), "YEAR"] = 2020

    return df_out