def METHOD_NAME(dfs: List[pd.DataFrame]) -> pd.DataFrame:
    """Merge all datasets"""
    df = pd.concat(dfs, ignore_index=True)
    # Fix variant name
    df.loc[df.year < YEAR_SPLIT, "variant"] = "estimates"
    # Index
    df = df.set_index(["location", "year", "metric", "sex", "age", "variant"])
    df = df.dropna(subset=["value"])
    # df = df.sort_index()
    return df