def abbreviate_statement(text):
    """Depending on the type of statement, abbreviate it to two letters
    and add a trailing underscore so it can be used as the first prefix
    of a title for an SQL table.
    """
    if text.find('income-statement') != -1:
        text = 'income statement'
        return text
    elif text.find('balance-sheet') != -1:
        text = 'balance sheet'
        return text
    elif text.find('cash-flow') != -1:
        text = 'cash flow'
        return text
    else:
        text = 'unknown'
        return text