def METHOD_NAME() -> "CountyToCBSAAggregator":
    """Creates a new object using data in the data/ dir."""
    df = pd.read_excel(
        dataset_utils.REPO_ROOT / CBSA_LIST_PATH,
        header=2,
        convert_float=False,
        dtype={"FIPS State Code": str, "FIPS County Code": str},
    )
    df[CommonFields.FIPS] = df["FIPS State Code"] + df["FIPS County Code"]
    df = df.loc[df[CommonFields.FIPS].notna(), :]
    dups = df.duplicated(CommonFields.FIPS, keep=False)
    if dups.any():
        raise ValueError(f"Duplicate FIPS:\n{df.loc[dups, CommonFields.FIPS]}")
    county_map = df.set_index(CommonFields.FIPS)["CBSA Code"].to_dict()
    cbsa_title_map = (
        df.loc[:, ["CBSA Code", "CBSA Title"]]
        .drop_duplicates()
        .set_index("CBSA Code", verify_integrity=True)["CBSA Title"]
        .to_dict()
    )
    return CountyToCBSAAggregator(county_map=county_map, cbsa_title_map=cbsa_title_map)