def deltawords(num, arg):
    """An adverb to come after the word 'improved' or 'slipped'"""
    delta = abs(num - arg)
    # We only pick out changes over 10%; over 30% in 9 months is unheard of.
    if delta == 0:
        word = "not at all"
    elif delta < 10:
        word = "slightly"
    elif delta < 20:
        word = "moderately"
    elif delta < 30:
        word = "considerably"
    else:
        word = "massively"
    return word