人口寿命是否统计infant mortality, 这个差别与infant mortality的关系不是线性的，

确实还要严重受到生育率的影响。

幼儿是死亡率比较高的人群，所以一个出生率比较低的国家，它的平均寿命自然就要高一些。所以中国人均寿命提高的很大一部分原因在于出生率的大幅度下降，这种进展实际是虚的。

感兴趣的可以调下面MATLAB程序的前三个参数。

引用：

%% Parameters
RateFertility = 3.0; %(lower than 1.5 for China since 2000)
AverageFertilityAge = 25; %(28 for China)
MortalityNewBirth = 100/1000; %(32/1000 for China at year 2000)

MaxAge = 99;
Age = (0:1:MaxAge)';

% Set mortality by age
Mortality = zeros(size(Age));
Mortality(1:20) = MortalityNewBirth * 1.7 .^(-(1:1:20)+1); % mortality of younger, decay with age
Mortality(end-floor(MaxAge/2):end) = 1.2 .^(-(floor(MaxAge/2):-1:0)); % mortality of aged, increase with age

plot(Age, Mortality)

%% Calculation
NumNewBirth = 1;
NumAtBirth = NumNewBirth * (RateFertility/2).^(-Age/AverageFertilityAge); % by age
NumLive = NumAtBirth .* (cumprod(1-Mortality)); % by age

BirthRate = NumNewBirth/sum(NumLive)

LifeSpan = sum(Age .* NumLive .* Mortality)/sum(NumLive .* Mortality)
LifeSpanNoInfantMortility = sum(Age(2:end) .* NumLive(2:end) .* Mortality(2:end))/sum(NumLive(2:end) .* Mortality(2:end))