def _get_default_annual_spacing(nyears):
    """
    Returns a default spacing between consecutive ticks for annual data.
    """
    if nyears < 11:
        min_spacing, maj_spacing = 1, 1
    elif nyears < 20:
        min_spacing, maj_spacing = 1, 2
    elif nyears < 50:
        min_spacing, maj_spacing = 1, 5
    elif nyears < 100:
        min_spacing, maj_spacing = 5, 10
    elif nyears < 200:
        min_spacing, maj_spacing = 5, 25
    elif nyears < 600:
        min_spacing, maj_spacing = 10, 50
    else:
        factor = nyears // 1000 + 1
        min_spacing, maj_spacing = factor * 20, factor * 100
    return min_spacing, maj_spacing
