Relative PPP
相對購買力平價

• Relative PPP suggests that changes in the exchange rate should reflect changes in prices
相對購買力平價，匯率的變化應該反映價格變動
• The country with the higher inflation rate has a depreciating currency
該國的通脹率上升，貨幣貶值
  $/£S0 x [(1+if) / (1+i)] = $/£St
Where:
$/£S0 = $ per £ exchange rate at time 0
$/£St = Exchange rate at time t
i, if = expected inflation in UK, US
[(1+if) / (1+i)] >1 if US inflation > UK inflation – and this will mean US citizens need more $s to buy £1

Questions Relative PPP
相對購買力平價問題

For the following examples (1&2), what will the spot exchange rate be in one year according to relative PPP if:
對于下面的例子（1＆2），什么的即期匯率將在一年內根據相對購買力平價，如果：
• The spot exchange rate is $2 per £ today, expected inflation in the UK is 5% and in the USA is 3%?
即期匯率是2元每英鎊今天，在英國的通脹預期是5％，而在美國為3％？
• The spot exchange rate is $2 per £ today, expected inflation in the UK is 4% and in the USA is 5%?
即期匯率是2元每英鎊今天，在英國的通脹預期為4％，在美國是5％嗎？
• Invert the formula for relative PPP so that it would be accurate for exchange rates quoted ‘in reverse’, i.e. number of £’s per $.
反轉相對購買力平價的計算公式，所以，這將是準確的匯率報價'反向'，即英鎊的每一美元。

Does PPP apply?
PPP是否適用？
http://ukthesis.org/gjswglzy

• There appears to be little evidence of PPP in the real world data, generally… why not?
有似乎是在現實世界中的數據，一般很少有證據的PPP......為什么不呢？
– PPP assumes that both countries record their prices with identical indexes – is this likely?
PPP假定，這兩個國家具有相同的索引記錄他們的價格 - 這是可能的嗎？
• National variation in statistical practice
國家在統計實踐中的變化
• National variation in the proportions of income people spend on certain goods – so weights vary
國家對某些商品消費收入人群的比例變化 - 這樣的權重各不相同
– Non-traded goods:
非貿易品：
• Balassa (1964) and Samuelson (1964) both thought
巴拉薩（1964）和薩繆爾森（1964）都認為
– the proportion of non-traded goods in the index would cause differences – and the proportion of such goods could vary between countries.  Can you export a haircut? #p#分頁標題#e#
非貿易商品在指數的比重會造成差異 - 此類商品的比例可能會有所不同的國家之間。你能出口理發？
– Transport costs varied due to ‘inherited’ characteristics such as location.
– 運輸成本不同，由于'繼承'的特征，如位置
• There could be significant differences due to these
由于這些有可能是顯著的差異
• Similarly, IRP is often not quite followed by real exchange rates:
同樣，IRP往往不太其次是實際匯率：
– Foreign or domestic capital movement is often restricted by governments, or is influenced by taxes on the exchange.
外國或國內的資本流動往往是由政府的限制，或受稅收上的交流。
– Whilst this makes obvious impacts on capital mobility and therefore IRP, the RISK of such controls being imposed is an additional deterrent to capital mobility even where it does not currently exist
雖然這明顯影響資本流動，因此IRP，被強加的風險控制資本流動是一個額外的威懾力，即使它目前不存在

Long-run conditions
長期運行條件

• Relative purchasing power parity holds better than PPP itself, and holds relatively well in the long run, although it is unlikely to precisely hold in any one period.
相對購買力平價成立優于PPP本身，從長遠來看持有相對較好，雖然這是不可能精確地保持在任何一個時期。
• CIP does seem to almost hold, but interest rates are almost always slightly out:  many international firms are ready to move their borrowing in response to this (causing arbitrage effects) so that it does generally hold as an approximate condition
CIP似乎幾乎持有，但利率幾乎總是稍微：許多國際公司已準備好將他們的借貸反應（導致套利效果）的，所以，它并普遍認為作為一個近似條件

Answers Relative PPP
相對購買力平價答案

Remember:
  $/£S0 x [(1+if) / (1+i)] = $/£St
1. St = $2 x [ 1.03 / 1.05 ] = $1.96
2. St = $2 x [ 1.05 / 1.04 ] = $2.02
3. Invert the main part of the formula [(1+if) / (1+i)] so..
 £/$S0 x [(1+i) / (1+if)] = £/$St
(this is actually the form used in Eaker et al., as it is American)

Alternatives to forward exchange?
遠期外匯的替代品？

• Loans can also be used to avoid the forward exchange problem.  E.g.  A company is owed $200,000 which will be repaid in 6 months.  The company can…
貸款也可以用來避免遠期外匯問題。例如A公司欠下200,000美元，而且將在6個月內償還。該公司可以...
– Find a forward exchange contract to fix a certain price on the movement of $200,000 into £s in 6 months; or#p#分頁標題#e#
查找遠期外匯合約?為英鎊200,000元的運動解決一定的價格在6個月內;
– Borrow $(200,000-6 months interest charge) now and bring it home, leaving the $200,000 repayment to you, to repay the loan you have taken out in the US.  This would leave you with
借用$（200,000-6個月的利息費用），并把它帶回家，留下20萬美元償還給你，你已經增加了在美國償還貸款。這將使你
• $200,000.(1-(rUS/2)).S£/$.

Sources
來源

• Allen, L. (1997)  Capital Markets and Institutions:  a global view.  (London:  Wiley)
• Eaker, M.R., Fabozzi, F.J., & Grant, D. (1996)  International Corporate Finance.  (International Ed., London:  Dryden) Chapters 4-5