With typical use, about 27 percent of women who use the withdrawal method experience an unintended pregnancy within the first year of use (4 percent with perfect use).

用典型使用的方法，大约有27%的有过撤回方法经历的女性在第一年的使用中意外怀孕(而完美使用的这一比例为4%)。

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It has been verified that the prediction effect of the method is sound by predicting average sunspot Numbers per year, which is a typical statistical model.

通过对年平均太阳黑子数典型统计模型的预测，验证了该方法的预测效果。

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