Add reform modifying brackets of a scale

CHANGELOG.md

@@ -1,7 +1,16 @@
+# 1.1.0 - [#7](https://github.com/openfisca/country-template/pull/7)
+
+* Tax and benefit system evolution: add a reform modifying the brackets of a scale
+* Impacted periods: from 2013-01-01
+* Impacted areas: `openfisca_country_template/parameters/taxes.xml`
+* Details:
+  - Show how to add, modify and remove a bracket.
+  - Add corresponding tests.
+
 # 1.0.0 - [#4](https://github.com/openfisca/country-template/pull/4)
 
 * Tax and benefit system evolution.
-* Impacted periods: all. 
+* Impacted periods: all.
 * Impacted areas:
   - `benefits`
   - `demographics`

README.md

@@ -37,6 +37,8 @@ These elements are described in different folders. All the modelling happens wit
 
 - The rates are in the `parameters` folder.
 - The formulas are in the `variables` folder.
+- This country template comes also with *reforms* in the `reforms` folder. This is optional: your country may exist without defining any reform.
+    - In this country, there is [a reform project](./openfisca_country_template/reforms/modify_social_security_taxation.py) aiming to modify the social security taxation, deleting the first bracket, raising the intermediary ones and adding a new bracket with a higher tax rate of `40 %` for people earning more than `40000`. This reform project would apply starting from `2017-01-01`.
 
 The files that are outside from the `openfisca_country_template` folder are used to set up the development environment.
 

openfisca_country_template/reforms/modify_social_security_taxation.py

@@ -0,0 +1,43 @@
+# -*- coding: utf-8 -*-
+
+# This file defines a reform.
+# A reform is a set of modifications to be applied to a reference tax and benefit system to carry out experiments.
+# See https://doc.openfisca.fr/reforms.html
+
+
+# Import from openfisca-core the common python objects used to code the legislation in OpenFisca
+from openfisca_core.model_api import *
+
+
+class modify_social_security_taxation(Reform):
+    # A reform always defines an `apply` method that builds the reformed tax and benefit system from the reference one.
+    # See https://doc.openfisca.fr/coding-the-legislation/reforms.html#writing-a-reform
+    def apply(self):
+        # Our reform modifies the `social_security_contribution` parameter, which is a scale.
+        # This parameter is declared in `taxes.xml` using a `<BAREME>` XML element, the French name for "scale".
+        #
+        # See https://doc.openfisca.fr/coding-the-legislation/legislation_parameters.html
+        self.modify_legislation_json(modifier_function=self.modify_brackets)
+
+    def modify_brackets(self, reference_legislation_json_copy):
+        # This function takes an argument `reference_legislation_json_copy` which is a JSON-like representation
+        # of the XML element. It can be modified and must be returned.
+
+        # Access the right legislation node:
+        scale = reference_legislation_json_copy['children']['taxes']['children']['social_security_contribution']
+        brackets = scale['brackets']
+
+        # Add 0.1 to the rates of the second bracket, keeping the same thresholds:
+        for rate in brackets[1]['rate']:
+            rate['value'] += 0.1
+
+        # Remove the first bracket:
+        del brackets[0]
+
+        # Add a new bracket with a higher tax rate for rich people:
+        brackets.append({
+            'rate': [{'start': '2017-01-01', 'value': 0.4}],
+            'threshold': [{'start': '2017-01-01', 'value': 40000}]
+            })
+
+        return reference_legislation_json_copy

openfisca_country_template/tests/reforms/modify_social_security_taxation.yaml

@@ -0,0 +1,30 @@
+# Test files describe situations and their expected outcomes
+# We can run this test on our command line using `openfisca-run-test modify_social_security_taxation.yaml`
+
+# This test is a partial adaptation of `social_security_contribution.yaml` to match the modifications introduced by the reform of the same name.
+
+# Note the `reforms: ` key in the below YAML blocks.
+
+- name: No social security contribution on small salaries
+  reforms: openfisca_country_template.reforms.modify_social_security_taxation.modify_social_security_taxation
+  period: 2017-01
+  input_variables:
+    salary: 2000
+  output_variables:
+    social_security_contribution: 0
+
+- name: Increased social security contribution on medium salaries
+  reforms: openfisca_country_template.reforms.modify_social_security_taxation.modify_social_security_taxation
+  period: 2017-01
+  input_variables:
+    salary: 15000
+  output_variables:
+    social_security_contribution: 1336
+
+- name: High social security contribution on high salaries
+  reforms: openfisca_country_template.reforms.modify_social_security_taxation.modify_social_security_taxation
+  period: 2017-01
+  input_variables:
+    salary: 50000
+  output_variables:
+    social_security_contribution: 8336

setup.py

@@ -7,7 +7,7 @@
 
 setup(
     name='OpenFisca-Country-Template',
-    version='1.0.0',
+    version='1.1.0',
     author='OpenFisca Team',
     author_email='contact@openfisca.fr',
     description=u'OpenFisca tax and benefit system for Country-Template',