貧窮門檻

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貧窮門檻是為滿足生活標準而需的最低收入水平。一如貧窮的認定，在已發展國家裡貧窮門檻（如美國）的認定標準明顯比第三世界高

如何釐定貧窮門檻時常引起廣泛討論。實際上，不同國家都有不同的貧窮門檻，但普遍來說他們都會利用單一貧窮門檻來比較經濟福利程度。在比較國際間的貧窮時常以購買力平價為基準，避免貧窮門檻因兌換率改變。因此「以少於一美元生活一天」解釋為「一天內購買貨物及服務的總開支少於在美國以一美元所能購買貨物及服務」（自行生產的貨物及服務也計算在內）。

幾乎所有社會都有貧窮的民眾。貧窮門檻是有用的經濟工具來作量度，來考慮是否利用福利、失業保險去減少貧窮。

釐定貧窮門檻須要找出所有必需品總開支，即成人一年開支的平均數。此方法是評估能夠維持可忍受的生活的最少開支。其基礎源自美國貧窮門檻，並隨通貨膨脹上升。在發展中國家，最昂貴的開支常是房屋租金。因為它對貧窮門檻有很大影響，經濟師常常留意房地產市場及住屋價格。

對於不同情況，個別因素也會考慮，譬如是否單親，是否年老幼小，婚姻狀況等等。

[编辑] 使用貧窮門檻的問題

使用貧窮門檻會有很多問題。因為收入僅僅高於或僅僅低於貧窮門檻對當事人沒有什麼差別，貧窮的影響效果是漸進式而並非割裂式，同樣的低收入對不同人有不同影響。為了克服這個困難，有時候需要利用收入不平等度量。

貧窮門檻倚靠對收入數字上量度。如果也考慮其他人類發展指標如健康、教育，它們也要量化，但這不是一個簡單的工作。

[编辑] 現金收入及福利

Rea Hederman, a senior policy analyst in the Center for Data Analysis at the Heritage Foundation, in the United States, wrote,

The official poverty measure counts only monetary income. It considers antipoverty programs such as food stamps, housing assistance, the Earned Income Tax Credit, Medicaid and school lunches, among others, "in-kind benefits" -- and hence not income. So, despite everything these programs do to relieve poverty, they aren't counted as income when Washington measures the poverty rate. [1]

[编辑] 貧窮線的定義

Poverty thresholds can be defined in different ways:

Social Security benefit based. If a government guarantees to make income up to some particular level then it may be presumed that that level is the poverty threshold. This is a problematic definition, because an uncharitable government may reduce the guaranteed income, thus reducing the incidence of poverty so defined while increasing the incidence of actual poverty.
A relative income line, related to some fraction of typical incomes. This excludes the wealthiest individuals from the calculation. For example, the OECD and the European Union uses 60% of national median equivalised household income.
A relative figure fixed in time and only adjusted for inflation - thus avoiding the possibility that if income inequality increases, then poverty may otherwise also increase.
When the World Bank calculates its "$1 a day" statistics, it uses a poverty threshold.

[编辑] 絕對貧窮

A measure of absolute poverty quantifies the number of people below a poverty threshold, and this poverty threshold is independent of time and place. For the measure to be absolute, the line must be the same in different countries. Such an absolute measure should look only at the individual's power to consume and it should be independent of any changes in income distribution. Such a measure is only possible when all consumed goods and services are counted and when PPP-exchange rates are used (see purchasing power parity). The intuition behind an absolute measure is that mere survival takes the same amount of goods across the world and that everybody should be subject to the same standards if meaningful comparisons of policies and progress are to be made. Notice that if everyone's real income in an economy increases, and the income distribution does not change, absolute poverty will decline.

Furthermore, the rate of absolute poverty can decline even though inequality is increasing - as long as the poorest get a higher real income than they had before.

This type of measure is often contrasted with measures of relative poverty (see below), which classify individuals or families as "poor" not by comparing them to a fixed cutoff point, but by comparing them to others in the population under study. (The term absolute poverty is also sometimes used as a synonym for extreme poverty.)

[编辑] 相對貧窮

主条目：相對剝削

A measure of relative poverty defines "poverty" as being below some relative poverty threshold. An example is when poverty is defined as households who earn less than 25% of the median income is a measure of relative poverty. Notice that if everyone's real income in an economy increases, but the income distribution stays the same, relative poverty will also stay the same.

Measures of relative poverty are almost the same as measuring inequality: If a society gets a more equal income distribution, relative poverty will fall. Following this, some argue that the term 'Relative Poverty' is itself misleading and that 'Inequality' should be used instead. They point out that if society changed in a way that hurt high earners more than low ones, then 'relative poverty' would decrease but every citizen of the society would be worse off. Likewise in the reverse direction: over the last few centuries, many countries have lowered their absolute poverty while increasing their relative poverty.

The phrase relative poverty can also be used in a different sense to mean "moderate poverty" – for example, a standard of living or level of income that is high enough to satisfy basic needs (like water, food, clothing, shelter, and basic health care), but still significantly lower than that of the majority of the population under consideration.