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This template takes a <tt>[[List of country codes|country_code]]</tt>, for example, "<tt>US</tt>" for the [[United States]] or "<tt>UK</tt>" for [[United Kingdom]], a <tt>value</tt> in that country's currency, a <tt>start_year</tt>, and applies to it the country's [[consumer price index|consumer price inflation]] until "recently".<ref>How recently depends on how the data set for each countries is constructed, and on the internal tables being updated accordingly every January. Some data tables provide inflation data up to December 31, {{#expr:{{CURRENTYEAR}}-1}}, others up to roughly June-July {{#expr:{{CURRENTYEAR}}-1}}, and others yet up to December 31, {{#expr:{{CURRENTYEAR}}-2}}.</ref> This means that whenever a new year arrives, all articles using this template have their displayed values updated accordingly.

Alternatively, you can provide a second, optional <tt>end_year</tt> parameter, and the value will be inflated for the period between the two years, providing a convenient way of getting values from different time periods adjusted around the same date.

=== Usage ===

 {{tlx|Inflation|country_code|value|start_year|r{{=}}digit}}
 {{tlx|Inflation|country_code|value|start_year|end_year|r{{=}}digit}}

Where:

* '''country_code''' and its minimum '''start_year''' can be any of the following:

{|class="wikitable sortable"
! ''Country name'' !! <tt>country_code</tt> !! <tt>start_year</tt>
|-
| [[Germany]]{{inflation-fn|DE}}        || align="center" | '''DE''' || align="center" | 1882
|-
| [[United Kingdom]]{{inflation-fn|UK}} || align="center" | '''UK''' || align="center" | 1264
|-
| [[United States]]{{inflation-fn|US}}  || align="center" | '''US''' || align="center" | 1800
|}

* '''end_year''', if provided, must be higher (later) than '''start_year''', but not higher than the current year, and will default to "recently" if left out;
* '''r='''''digit'' sets the digit in which the value must be rounded, defaulting to "0" if unspecified, i.e., without cents (see [[Template:Inflation#Tips & Tricks|Tips & Tricks]] below for details on how to use this parameter).

Examples:

* {{aye}} {{tlx|Inflation|DE|1000000|2000}} = {{Inflation|DE|1000000|2000}}
* {{aye}} {{tlx|Inflation|US|1000000|2001|2001}} = {{Inflation|US|1000000|2001|2001}}
* {{aye}} {{tlx|Inflation|US|1000000|1990|2005|r{{=}}2}} = {{Inflation|US|1000000|1990|2005|r=2}}
* {{aye}} {{tlx|Inflation|UK|1000000|1323|1978|r{{=}}-3}} = {{Inflation|UK|1000000|1323|1978|r=-3}}

Entering invalid parameters will result in a link to the [[NaN]] article:

* {{nay}} {{tlx|Inflation}} = {{Inflation}}
* {{nay}} {{tlx|Inflation|abc}} = {{Inflation|abc}}
* {{nay}} {{tlx|Inflation|DE|1000000}} = {{Inflation|DE|1000000}}
* {{nay}} {{tlx|Inflation|US|1000000|1200|3000}} = {{Inflation|US|1000000|1200|3000}}
* {{nay}} {{tlx|Inflation|UK|1000000|2005|2004}} = {{Inflation|UK|1000000|2005|2004}}

==== Tips & Tricks ====
===== Currency conversion =====

This template is currency agnostic, what means it doesn't convert between different currencies. Thus, if you wanted to know how much DM 1,000.00 marks in 1960 are worth nowadays, entering {{tlx|Inflation|DE|1000|1960|r{{=}}2}} would provide a result (''{{Inflation|DE|1000|1960|r=2}}'') still in marks, not in euros.

Consequently, if you need a result in another currency than the one in which the original value is stated, for now you must do the conversion manually, as in the following example which uses the defined conversion rate of €&nbsp;1 = DM&nbsp;1.95583:

* {{aye}} <tt><nowiki>{{#expr:</nowiki>({{tlx|Inflation|DE|1000|1960|r{{=}}2}}<nowiki> / 1.95583) round 2}}</nowiki></tt> = {{#expr:({{Inflation|DE|1000|1960|r=2}} / 1.95583) round 2}}

A currency conversion template to ease these conversion tasks is planned. This section will be updated accordingly once it's developed.

===== Rounding =====

By default the values are calculated to the unit, as for most huge values cents are undesirable. If you need a different precision you can provide the {{para|r}} parameter to determine in which digit the rounding must happen. To obtain cents you'd use {{para|r|2}}, but other values can be used, including negative ones: {{para|r|-3}}, for example, will round to the nearest thousand, {{para|r|-6}} to the nearest million, and so on and so forth.

===== Formatnum =====

For a better visualization you can format the returned value using either the internal <tt><nowiki>{{</nowiki>[[Help:Magic words#Formatting|formatnum:]]<nowiki>}}</nowiki></tt> magic word, or the alternative {{tlx|Formatprice}} template ([[Template:Inflation#Formatprice|see below]]). Each method has its advantages and disadvantages.

<tt><nowiki>{{</nowiki>[[Help:Magic words#Formatting|formatnum:]]<nowiki>}}</nowiki></tt> is the standard method for formatting numbers in MediaWiki. It add thousands and decimal separators according to the user settings, and works well for raw numbers composed of up to 15 digits and a dot. On the other hand, it doesn't allow one to set how many digits ''must'' be shown after the decimal dot. Thus, a calculated value of "1234.5" will appear as "{{formatnum:{{#expr:1000 + 234.5}}}}", not the expected "1,234.50", making it better suited for integer prices unless the value is known and you can add the missing zeros by hand:

* {{aye}} <tt>'''DM''' <nowiki>{{formatnum:</nowiki>{{tlx|Inflation|DE|1000000|1957|1978}}<nowiki>}}</nowiki>'''.00'''</tt> = DM {{formatnum:{{Inflation|DE|1000000|1957|1978}}}}.00
* {{aye}} <tt>'''£'''<nowiki>{{formatnum:</nowiki>{{tlx|Inflation|UK|1000000|1323|1978|r{{=}}-4}}<nowiki>}}</nowiki></tt> = £{{formatnum:{{Inflation|UK|1000000|1323|1978|r=-4}}}}
* {{aye}} <tt>'''$'''<nowiki>{{formatnum:</nowiki>{{tlx|Inflation|US|1000000|1990|r{{=}}2}}<nowiki>}}</nowiki></tt> = ${{formatnum:{{Inflation|US|1000000|1990|r=2}}}}

Another potential source of difficulties resides in the way certain calculated values are expressed. In many cases the result comes as a number in engineering units ("1.2E+9" instead of "1200000000"), and when that happens <tt><nowiki>{{</nowiki>[[Help:Magic words#Formatting|formatnum:]]<nowiki>}}</nowiki>'ing</tt> the result fails. A workaround then is to express the value to be inflated with less digits, adding a multiplier text such as "million" after the result, and then hitting the "Show preview" button as many times as needed, changing parameters until the best result is found:

* {{nay}} <tt>'''$'''<nowiki>{{formatnum:</nowiki>{{tlx|Inflation|US|1000000000|1900|r{{=}}-8}}<nowiki>}}</nowiki></tt> = ${{formatnum:{{Inflation|US|1000000000|1900|r=-8}}}}
* {{nay}} <tt>'''$'''<nowiki>{{formatnum:</nowiki>{{tlx|Inflation|US|1000000|1900|r{{=}}-5}}<nowiki>}}</nowiki> ''thousand''</tt> = ${{formatnum:{{Inflation|US|1000000|1900|r=-5}}}} thousand
* {{aye}} <tt>'''$'''<nowiki>{{formatnum:</nowiki>{{tlx|Inflation|US|1000|1900|r{{=}}-2}}<nowiki>}}</nowiki> ''million''</tt> = ${{formatnum:{{Inflation|US|1000|1900|r=-2}}}} million
* {{aye}} <tt>'''$'''<nowiki>{{formatnum:</nowiki>{{tlx|Inflation|US|1|1900|r{{=}}1}}<nowiki>}}</nowiki> ''billion''</tt> = ${{formatnum:{{Inflation|US|1|1900|r=1}}}} billion

The following section provides an automated way of avoiding this trial and error scenario.

===== Formatprice =====

{{tlx|Formatprice}} is a template specifically designed to display price values, both big and small, in a more pleasant way than <tt><nowiki>{{</nowiki>[[Help:Magic words#Formatting|formatnum:]]<nowiki>}}</nowiki></tt> allows for. For example, instead of showing the whole of a huge number such as "953,783,409,856.12", it would show it as "{{Formatprice|953783409856.12}}", while small numbers have their cents part appearing as expected, "1234.5" being properly shown as "{{Formatprice|1234.5}}".

On the down side, {{tlx|Formatprice}} has no built-in intelligent handling of user locale settings, what means that some users might see a dot or a comma the opposite way they'd expect. As a general rule of thumb this shouldn't be a serious concern though, as most numbers in Wikipedia are hand-written anyway and will show as entered regardless of user settings.

* {{aye}} <tt>'''DM''' <nowiki>{{</nowiki>[[Template:Formatprice|Formatprice]]<nowiki>|</nowiki>{{tlx|Inflation|DE|1000000|1957|1978}}<nowiki>}}</nowiki></tt> = DM {{Formatprice|{{Inflation|DE|1000000|1957|1978}}}}
* {{aye}} <tt>'''£'''<nowiki>{{</nowiki>[[Template:Formatprice|Formatprice]]<nowiki>|</nowiki>{{tlx|Inflation|UK|1000000|1323|1978|r{{=}}-4}}<nowiki>}}</nowiki></tt> = £{{Formatprice|{{Inflation|UK|1000000|1323|1978|r=-4}}}}
* {{aye}} <tt>'''$'''<nowiki>{{</nowiki>[[Template:Formatprice|Formatprice]]<nowiki>|</nowiki>{{tlx|Inflation|US|1000000|1990|r{{=}}2}}<nowiki>}}</nowiki></tt> = ${{Formatprice|{{Inflation|US|1000000|1990|r=2}}}}
* {{aye}} <tt>'''$'''<nowiki>{{</nowiki>[[Template:Formatprice|Formatprice]]<nowiki>|</nowiki>{{tlx|Inflation|US|1000000000|1900|r{{=}}-8}}<nowiki>}}</nowiki></tt> = ${{Formatprice|{{Inflation|US|1000000000|1900|r=-8}}}}

===== Documenting =====

It's a good practice to provide a valid reference for the prices calculated with this template in the articles where it's used. The template {{tl|Inflation-fn|country}} was developed to ease this task. It accepts as its single parameter the same country codes used here, and will generate one or more appropriate footnotes. Typically, this is how a piece of text using it looks like:

* <tt><nowiki>In 1910 a ''blah'' cost on average £1,000. This is equivalent to £{{Formatprice|{{Inflation|</nowiki>'''UK'''<nowiki>|1000|1910|r=2}}}} in present day </nowiki>{{Nowrap|terms.<nowiki>{{Inflation-fn|</nowiki>'''UK'''<nowiki>}}</nowiki>}}</tt>

Resulting in this converted code (notice the footnote link at the end):

* In 1910 a ''blah'' cost on average £1,000. This is equivalent to £{{Formatprice|{{Inflation|UK|1000|1910|r=2}}}} in present day terms.{{Inflation-fn|UK}}

The footnote thus generated appears whenever {{tlx|reflist}} or <tt><nowiki><references /></nowiki></tt> is used in an article, usually in its "References" section. See below for the live example in this document's own [[Template:Inflation#References|References]] section, or click the above generated footnote to jump to it.

==== Limitations ====

#Currently it isn't possible to "de-inflate" a value to what it would have been in a previous year. If you need this functionality, please request it at the [[Template talk:Inflation|talk page]]. Adding it won't be difficult, but there's no point in doing so before someone actually needs it.
#[[Wikipedia:Template substitution|Substitution]] isn't supported at all. Trying to <tt><nowiki>{{subst:</nowiki>[[Template:Inflation|Inflation]]<nowiki>|...}}</nowiki></tt> would only result in a long sequence of embedded parser code without any direct benefit. If you need to obtain an inflated price only once, please use the special [[Special:ExpandTemplates|ExpandTemplates]] page then copy the result and paste it at the desired location.

=== References ===
{{reflist}}

=== See also ===

* {{tl|Inflation-fn}}
* {{tl|Formatprice}}
* [[Inflation]]
* [[Consumer price index]]
* [[Harmonised Index of Consumer Prices]]
* [[List of country codes]]
* [[List of circulating currencies]]
* [[United States Consumer Price Index]]
* [[Consumer Price Index (United Kingdom)]]

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