def count_to_half(array):
    """Determination of half-initial value index

    Return first index at which array values decrease below 1/2 of
    the initial initial value `array[0]`.
    """
    num = 0
    for item in array[1:]:
        if item < array[0] / 2:
            break
        else:
            num += 1
    return num
