这样是否会导致男女比例失衡?

网上谈论到当今社会男女比例失调，有人说到一个问题，某些地方政策是，夫妻俩生育一个孩子后，如果是女的就可以再生一个，如果是男的，就不能继续了。这导致了男女比例失调。 然而，立马有人反对说，这件事对全社会影响比例非常小。

Argue is cheap, show me the code!

我做了一个简单的模拟器，模拟这个事情，看结果就完了。 具体设定如下：

• 每个人到20岁开始寻找伴侣，到60生命结束
• 新生儿男女比例都是1/2
• 生下女儿则两年后继续尝试，生下儿子则停止尝试(在此，我假定生育完一个孩子后要隔一年再来战过。)
• 如果生下五个女儿，也停止尝试(当然，如果夫妻有人死了自然不能继续生育了)
• 假定理想条件，年纪大优先找到另一半，但45岁后不再尝试

如此模拟200年(这个时间我随便写的，修改个变量就是2000年也很容易)，输出:

• 终身未娶/未嫁和成功完婚的数量
• 在世的男女比例
• 在世未婚的男女比例

为了代码方便，使用了这样一些假定如下以hard code放里面了。

• 假定开始时间是2014年
• 开始时刚出生的男女人数相同

模拟器构造了几个队列，分别表示男孩，女孩，夫妻和FA的筒子们，每年对生孩子，结婚和死亡分别统计。生下的孩子性别用随机数roll个，每年统计下各个队列里面的信息即可。构造非常简单，它对我的最大困扰其实是自己手工实现个链式队列。

那么，你觉得这个政策影响大么？

附：直接给一个相关代码和参考结果吧，你看符合你预期吧。

import random
from collections import deque
import matplotlib.pyplot as plt
from tqdm import tqdm


class Person:
    """表示一个人的类，包含性别、出生年份、婚姻状态等属性"""

    def __init__(self, gender, birth_year):
        self.gender = gender  # 'M' for male, 'F' for female
        self.birth_year = birth_year
        self.married = False
        self.spouse = None  # 配偶引用
        self.children = 0  # 孩子总数
        self.last_child_year = None  # 最后一个孩子出生的年份
        self.daughters = 0  # 女儿数量

    def age(self, current_year):
        """计算当前年龄"""
        return current_year - self.birth_year

    def is_alive(self, current_year):
        """判断是否在世（假设60岁为寿命上限）"""
        return self.age(current_year) <= 60

    def can_marry(self, current_year):
        """判断是否可以结婚（20-45岁之间且未婚）"""
        return (
            not self.married
            and self.is_alive(current_year)
            and self.age(current_year) >= 20
            and self.age(current_year) < 45
        )

    def can_have_children(self, current_year):
        """判断是否可以生育孩子"""
        # 必须已婚且双方都在世
        if (
            not self.married
            or not self.is_alive(current_year)
            or self.spouse is None  # 防止spouse为None时访问is_alive方法
            or not self.spouse.is_alive(current_year)
        ):
            return False

        # 如果已经有儿子或5个女儿，则停止生育
        if self.children > 0 and self.daughters < self.children:
            return False
        if self.daughters >= 5:
            return False

        # 需要在上一个孩子出生后等待2年
        if self.last_child_year is not None and current_year - self.last_child_year < 2:
            return False

        # 女性年龄限制（20-45岁）
        if self.gender == "F" and (
            self.age(current_year) < 20 or self.age(current_year) > 45
        ):
            return False

        return True


class Couple:
    """表示一对夫妻的类"""

    def __init__(self, husband, wife, marriage_year):
        self.husband = husband
        self.wife = wife
        self.marriage_year = marriage_year
        # 更新双方的婚姻状态
        husband.married = True
        husband.spouse = wife
        wife.married = True
        wife.spouse = husband

    def is_active(self, current_year):
        """判断夫妻双方是否都在世"""
        return self.husband.is_alive(current_year) and self.wife.is_alive(current_year)

    def can_have_children(self, current_year):
        """判断夫妻是否可以生育（委托给妻子判断）"""
        return self.wife.can_have_children(current_year)

    def have_child(self, current_year):
        """生育一个孩子，50%概率为男孩或女孩"""
        # 50% chance for each gender
        gender = "M" if random.random() < 0.5 else "F"

        # 更新父母的孩子信息
        self.husband.children += 1
        self.wife.children += 1
        self.wife.last_child_year = current_year

        if gender == "F":
            self.husband.daughters += 1
            self.wife.daughters += 1

        # 返回新生儿
        return Person(gender, current_year)


class Simulation:
    """人口模拟类，模拟人口变化、婚姻和生育"""

    def __init__(self, initial_population=1000, years=200, start_year=2014):
        self.current_year = start_year
        self.end_year = start_year + years

        # 初始化人口队列
        self.males = deque()  # 未婚男性
        self.females = deque()  # 未婚女性
        self.couples = deque()  # 已婚夫妻
        self.forever_alone_males = deque()  # 超过45岁未婚男性
        self.forever_alone_females = deque()  # 超过45岁未婚女性

        # 统计历史总人口
        self.total_males_ever = 0
        self.total_females_ever = 0
        # 统计历史 forever alone
        self.historical_forever_alone_males = 0
        self.historical_forever_alone_females = 0

        # 创建初始人口，男女比例相等
        for _ in range(initial_population // 2):
            # 随机年龄在0-60岁之间
            male_birth = self.current_year - random.randint(0, 60)
            female_birth = self.current_year - random.randint(0, 60)

            self.males.append(Person("M", male_birth))
            self.females.append(Person("F", female_birth))
            self.total_males_ever += 1
            self.total_females_ever += 1

        # 统计数据
        self.yearly_stats = []

    def run(self):
        """运行模拟"""
        for year in tqdm(
            range(self.current_year + 1, self.end_year + 1), desc="Simulating years"
        ):
            self.current_year = year

            # 处理死亡
            self.process_deaths()

            # 处理婚姻
            self.process_marriages()

            # 处理生育
            self.process_births()

            # 收集统计数据
            self.collect_stats()

        self.display_results()

    def process_deaths(self):
        """处理人口死亡（移除超过60岁的人）"""
        # 移除已经达到寿命上限的人
        self.males = deque([m for m in self.males if m.is_alive(self.current_year)])
        self.females = deque([f for f in self.females if f.is_alive(self.current_year)])
        self.forever_alone_males = deque(
            [m for m in self.forever_alone_males if m.is_alive(self.current_year)]
        )
        self.forever_alone_females = deque(
            [f for f in self.forever_alone_females if f.is_alive(self.current_year)]
        )

        # 更新夫妻列表，只保留双方都在世的夫妻
        active_couples = deque()
        for couple in self.couples:
            if couple.is_active(self.current_year):
                active_couples.append(couple)
        self.couples = active_couples

    def process_marriages(self):
        """处理婚姻匹配，年龄大的优先"""
        # 按年龄排序（年龄大的优先）
        marriageable_males = sorted(
            [m for m in self.males if m.can_marry(self.current_year)],
            key=lambda x: self.current_year - x.birth_year,
            reverse=True,
        )
        marriageable_females = sorted(
            [f for f in self.females if f.can_marry(self.current_year)],
            key=lambda x: self.current_year - x.birth_year,
            reverse=True,
        )

        # 匹配夫妻
        while marriageable_males and marriageable_females:
            husband = marriageable_males.pop(0)
            wife = marriageable_females.pop(0)

            # 从单身池中移除
            if husband in self.males:
                self.males.remove(husband)
            if wife in self.females:
                self.females.remove(wife)

            # 创建新的夫妻
            self.couples.append(Couple(husband, wife, self.current_year))

        # 将超过45岁的人加入"永远单身"列表
        for m in list(self.males):
            if m.age(self.current_year) >= 45 and not m.married:
                self.males.remove(m)
                self.forever_alone_males.append(m)
                self.historical_forever_alone_males += 1

        for f in list(self.females):
            if f.age(self.current_year) >= 45 and not f.married:
                self.females.remove(f)
                self.forever_alone_females.append(f)
                self.historical_forever_alone_females += 1

    def process_births(self):
        """处理生育"""
        for couple in self.couples:
            if couple.can_have_children(self.current_year):
                child = couple.have_child(self.current_year)
                if child.gender == "M":
                    self.males.append(child)
                    self.total_males_ever += 1
                else:
                    self.females.append(child)
                    self.total_females_ever += 1

    def collect_stats(self):
        """收集年度统计数据"""
        # 计算总人口
        total_males = (
            len(self.males)
            + len(self.forever_alone_males)
            + sum(1 for c in self.couples if c.husband.is_alive(self.current_year))
        )
        total_females = (
            len(self.females)
            + len(self.forever_alone_females)
            + sum(1 for c in self.couples if c.wife.is_alive(self.current_year))
        )

        # 计算未婚人口
        unmarried_males = len(self.males) + len(self.forever_alone_males)
        unmarried_females = len(self.females) + len(self.forever_alone_females)

        # 存储统计数据
        self.yearly_stats.append(
            {
                "year": self.current_year,
                "total_males": total_males,
                "total_females": total_females,
                "unmarried_males": unmarried_males,
                "unmarried_females": unmarried_females,
                "couples": len(self.couples),
                "forever_alone_males": len(self.forever_alone_males),
                "forever_alone_females": len(self.forever_alone_females),
            }
        )

    def display_results(self):
        """显示最终结果"""
        final_stats = self.yearly_stats[-1]

        print("\n=== Final Statistics ===")
        print(f"Year: {final_stats['year']}")
        print(
            f"Total population: {final_stats['total_males'] + final_stats['total_females']}"
        )
        print(
            f"Gender ratio (M:F): {final_stats['total_males']} : {final_stats['total_females']} = {final_stats['total_males'] / final_stats['total_females']:.2f}"
        )
        print(
            f"Unmarried gender ratio (M:F): {final_stats['unmarried_males']} : {final_stats['unmarried_females']} = {final_stats['unmarried_males'] / final_stats['unmarried_females'] if final_stats['unmarried_females'] > 0 else 'inf':.2f}"
        )
        print(f"Forever alone males: {final_stats['forever_alone_males']}")
        print(f"Forever alone females: {final_stats['forever_alone_females']}")
        print(f"Active couples: {final_stats['couples']}")

        # 新增：输出历史总人口及比例
        print("\n--- Historical Population (All Ever Born) ---")
        print(f"Total males ever born: {self.total_males_ever}")
        print(f"Total females ever born: {self.total_females_ever}")
        if self.total_females_ever > 0:
            print(f"Historical gender ratio (M:F): {self.total_males_ever} : {self.total_females_ever} = {self.total_males_ever / self.total_females_ever:.2f}")
        else:
            print("Historical gender ratio (M:F): inf")
        print(f"Historical Forever Alone Males: {self.historical_forever_alone_males}")
        print(f"Historical Forever Alone Females: {self.historical_forever_alone_females}")

        # 绘制性别比例随时间变化的图表
        self.plot_results()

    def plot_results(self):
        """绘制结果图表"""
        years = [stat["year"] for stat in self.yearly_stats]
        gender_ratios = [
            (
                stat["total_males"] / stat["total_females"]
                if stat["total_females"] > 0
                else 0
            )
            for stat in self.yearly_stats
        ]
        unmarried_ratios = [
            (
                stat["unmarried_males"] / stat["unmarried_females"]
                if stat["unmarried_females"] > 0
                else 0
            )
            for stat in self.yearly_stats
        ]

        plt.figure(figsize=(12, 6))

        # 绘制总体性别比例图
        plt.subplot(1, 2, 1)
        plt.plot(years, gender_ratios, "b-", label="Gender Ratio (M:F)")
        plt.axhline(y=1.0, color="r", linestyle="--", label="Equal Ratio")
        plt.title("Gender Ratio Over Time")
        plt.xlabel("Year")
        plt.ylabel("Ratio (M:F)")
        plt.legend()

        # 绘制未婚人口性别比例图
        plt.subplot(1, 2, 2)
        plt.plot(years, unmarried_ratios, "g-", label="Unmarried Ratio (M:F)")
        plt.axhline(y=1.0, color="r", linestyle="--", label="Equal Ratio")
        plt.title("Unmarried Gender Ratio Over Time")
        plt.xlabel("Year")
        plt.ylabel("Ratio (M:F)")
        plt.legend()

        plt.tight_layout()
        plt.savefig("gender_ratio_simulation.png")
        plt.show()


if __name__ == "__main__":
    # 运行模拟
    sim = Simulation(initial_population=10000, years=200, start_year=2014)
    sim.run()

参考结果：

=== Final Statistics ===
Year: 2214
Total population: 14688
Gender ratio (M:F): 7330 : 7358 = 1.00
Unmarried gender ratio (M:F): 2383 : 2411 = 0.99
Forever alone males: 0
Forever alone females: 0
Active couples: 4947

--- Historical Population (All Ever Born) ---
Total males ever born: 32943
Total females ever born: 32884
Historical gender ratio (M:F): 32943 : 32884 = 1.00
Historical Forever Alone Males: 1354
Historical Forever Alone Females: 1263