哥大教授Landrum B. Shettles和David M. Rorvik专门研究已婚夫妇应当如何通过ML方式和ML时间的选择来决定生男生女，N年前出版了一本专著《How to Choose the sex of Your Baby》，总结其在生育方面的研究成果，在国际上非常有名。今年偶然上网，发现amazon对此书好评如潮，而此书在goodreads上也获得较高评分，不少因此受益的亲身验证者回帖称赞，比如goodreads上回帖的读者，Shelves: “This book was awesome! After 3 boys & so many boys in my husband's family that it's borderline ridiculous, I am expecting a GIRL!!! I totally credit this book. I read the whole thing & followed the directions it gave, fully ready for either girl or boy, as long as I could say I tried on my last baby. It worked!”Elizabeth ：“I read this because after 2 girls, we really wanted a boy for number 3. Lucky for me, the ‘boy method’ is mostly about optimizing chances of getting pregnant. This book does have good information on fertility and how to tell when you are ovulating. We did get a boy. ”Lisa Shook：“Hey, it works! I had 3 girls first and read the book to have my son:) ”，还有amazon上回帖的读者：“ A Wonderful and Successful System - My wife read this book long before we attempted to have any children and I was skeptical. She explained the process, which is envolved. It was completely worth the effort to follow the formulas as described in the book. We now have four children, two older boys and two younger girls, exactly as planned. This book was 100% successful for us and our family.”等等，读者中的不同意见较为少见。
我曾经弄来一本，大概翻了一遍，深受启发。
精子可以分为男精子和女精子，各有其特性。“The male sperm is lighter, faster, and round headed. It is also more fragile and subject to heat, toxins, and other risk factors. The female sperm is slower but hardier with a more oval head.”简略而形象的说来，男精子就是缩微版本的男人，而女精子就是缩微版本的女人。男人和女人有何差别呢？男人外表强大、有力，实则不能久经考验，而女人长寿、生命力顽强持久。男精子活跃、暴发力强、游动速度快、气势汹汹，但是环境适应能力差，要么在某种性质的体内环境下存活时间短，要么在某种性质的体内环境下忽然就蔫了、游不动了，在长时竞争与长途竞争中多半要输，看上去很好很强大，但是却往往很容易夭折掉，也多见其半途而废，女精子反之。如此推断，可以得出一些较为确定的分析结果，比如通过排卵当日ML来缩短竞争时间则更有利于男精子竞争获胜；比如男方保持充沛的精力厚积薄发、女方需要得到更大满足则可缩短竞争路程，同样有利于男精子竞争获胜。当然书中说的更为详尽，只能引述其大概，恕不能一一例举。“TIMING is the single most important factor in sex selection. ”“Time intercourse for the day of ovulation, and if possible, within 12 hours. Even if intercourse takes place several hours before ovulation happens, but with a day of it, the odds are in favor of the male producing sperm.”“Your best chances for having a boy are in the 12 hours before ovulation occurs. But chances are still significant 24 hours before ovulation.”“Twelve hours before ovulation is ideal but anytime 24 hours before ovulation should increase chances for a boy.”“When trying for a girl, have sex daily from the time bleeding ends until the cutoff day – four, three, or two days before ovulation. Abstain from sex completely until a few days after ovulation has passed because intercourse may stimulate female secretions that favor male sperm.” “ Intercourse Recommendations: Dr. Shettles says the “missionary position” makes it less likely the male sperm will be deposited near the cervix. Shallow penetration will deposit the sperm in the more acidic vaginal canal, favoring the female sperm. Finally, the woman should avoid orgasm, if possible, so the alkaline secretions that favor male sperm will not emitted, nor will the orgasmic muscle contractions that help propel the sperm towards the egg.”
女权更高，女方更独立、个性更强的家庭，女方倾向于尊重自己的需要，男方倾向于尊重女方的需要，生男孩的概率更大，因为她们总是能够抓住女人最兴奋、状态最好的日子进行ML，而那一天往往就是女人的排卵日，而让女人最舒服的姿势，也就是精卵结合的过程最短的姿势。女人感应本能的需要，所选择的时间和姿势更容易生男孩。
受其启发，我忽然觉得：计划生育并非造成男女性别比失衡的原因。其原因在于男女地位的失衡。今日中国社会男多女少其实是因为新中国后妇女地位大幅度提高所导致的。
旧中国是一个男权社会，新中国革命后，几乎一下子就扭转了局面。众所周知，毛泽东提倡妇女半边天的说法，带来的结果是妇女占据了大半边天，也就是在以前有点天的基础上，让男人们让出了半边天，这就等于占据了大半边天。在这种情况下，就有点矫枉过正......
矫枉过正的后果就是，今日中国已经成为一个阴盛阳衰、乾坤颠倒、雌鸡司晨的女权社会。现实状况就是：女少男多，女人们全都成为经济学意义上的稀缺资源，见怪不怪的是，哪怕是一个且老且丑且肥已经离异N次的乡下女文盲，也要理直气壮的同时自由交往于多个男子以获取更多的经济支持，而遍布各地的光棍，虽然多半是一表人才、德行且佳，却终身无缘婚配。这样一种状况，很容易造成恶性循环，因为女权高，则女人们生女孩的概率更小，生男孩的概率更高，如此男孩更多女孩更少，女权便一代更比一代高了。更高的女权带来生育男孩的更高的概率，更多的男性则带来更高的女权，这种一代更比一代女孩少女权高的恶性循环，有一定的代际加速度。这是一种经济学原理与生物学原理共同作用下的恶性循环。
哎，作为男人，多希望遇到一个女多男少的性别比失衡的状况难以扭转的时代啊，每个男人都不得不娶上三妻四妾，以应付社会上妇女同胞严重供过于求的状况，真是生不逢时啊……