def boost_nph(group, nph):
    """
    Return a fraction of boost based on total number of high-binding peptides per IAR.

    :param pandas.core.frame.DataFrame group: The IAR under review.
    :param float nph: The total boost amount allotted to this criterion.
    :returns: The percent of boost provided by this criterion.
    :rtype: float

    >>> df = pandas.DataFrame({'binding_score': [0.1, 0.4, 1.5, 0.04, 0.44, 1.75, 1.0]})
    >>> boost_nph(df, 1)
    1.0
    >>> df = pandas.DataFrame({'binding_score': [0.1, 0.4, 1.5, 1.75, 1.0]})
    >>> boost_nph(df, 1)
    0.9
    >>> df = pandas.DataFrame({'binding_score': [0.1, 0.4, 1.5, 1.75]})
    >>> boost_nph(df, 1)
    0.7
    >>> df = pandas.DataFrame({'binding_score': [0.1, 1.5]})
    >>> boost_nph(df, 1)
    0.4
    >>> df = pandas.DataFrame({'binding_score': [1.5]})
    >>> boost_nph(df, 1)
    0.0
    """
    n = len(group[group['binding_score'] <= 1.0])
    return round(nph * ((n >= 1) * 0.4 + (n >= 2) * 0.3 + (n >= 3) * 0.2 + (n >= 4) * 0.1), 2)