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Opening up the French tax software
http://www.openfisca.fr/https://framagit.org/openfiscahttps://github.com/openfisca
@OpenFisca
Michel [email protected]
PyData – June 14, 2016
I - What is OpenFisca?
Legislation
It's growing!
In French (that most French people don't understand),
not in python!
NoticesBulletin Officiel des Finances
Publiques-Impôts (BOFiP)
Décrets
How to compute the French tax and benefits?
It's complex!
4
How to compute the French tax and benefits?
It's complex, because the reality is complex.
IndividualsHousingFamilyTaxation
How to compute the French tax and benefits?
OpenFisca aims to :● cover both tax and benefits policies● be efficient
● one family simulation● simulation on the whole country
● be understandable● be open source
What is OpenFisca?
OpenFisca is used for :● improving readability
to the public● designing reforms● simulating one's
situation● understanding the tax
and social system
mes-aides.gouv.fr
Why compute the French tax and benefits?
OpenFisca is used for :● improving readability
to the public● designing reforms● simulating one's
situation● understanding the tax
and social system
How to compute the French taxes ?
tax difference between/after marriage
OpenFisca is used for :● improving readability
to the public● designing reforms● simulating one's
situation● understanding the tax
and social system
How to compute the French taxes ?
personal simulationui.openfisca.fr
OpenFisca is used for :● improving readability
to the public● designing reforms● simulating one's
situation● understanding the
tax and social system
How to compute the French taxes ?
tax percentage as a function of income
The history of OpenFisca
2011 2014 2016
2 economists
python scripts with QT frontend
2 developers join the project
tax calculator of the tax administration
released
increasing demand for an open simulator
OpenFisca reaches the sky and beyond...
(see later)
France StratégieFrance StratégieIPPEtalab
II – The French tax calculator
● direct demand (aug 2014)● 6 months later : seisine of the CADA● 2 months later : positive notice from the CADA● 2 months later : beginning of judicial proceedings● 10 months later : release of the source code !● 10 months later + ε : the court issues a positive decision
The quest for the source code
(want to speed up the process ? → ouvre-boite.org)
● April 1-2, 2016 at the Mozilla Fundation● presence of 3 Ministers● developers, civil servants, economists,
citizens... all sitting at the same table !
A hackathon to celebrate : CodeImpôt
Preparation by Etalab and DGFiP :● understand the Domain Specific
Language (DSL) : M● parse using Clean PEG (Igor
Dejanović's Arpeggio)● simplify the Abstract Syntax Tree
(AST)
→ Direct Acyclic Graph of trees
Preparationregle 10214:application : iliad,batch ;CSGAC = max(0,CSGC CICSG);
CSNET = max(0,(CSGC + PCSG CICSG CSGIM)) ;
RDSAC = max(0,RDSC CIRDS);RDNET = max(0,(RDSC + PRDS
CIRDS CRDSIM));
PRSNET = max(0,(PRSC + PPRS CIPRS PRSPROV)) ;
CVNAC = CVNSALC;CVNNET = max(0,(CVNSALC + PCVN
COD8YT));
REGVNET = BREGV + PREGV ;
CDISAC = CDISC ;CDISNET = max(0,(CDISC + PCDIS
CDISPROV)) ;CGLOAAC = CGLOA ;CGLOANET = max(0,(CGLOA + PGLOA
COD8YL )) ;
Preparation by Etalab and DGFiP :● understand the Domain Specific
Language (DSL) : M● parse using Clean PEG (Igor
Dejanović's Arpeggio)● simplify the Abstract Syntax Tree
(AST)
→ Direct Acyclic Graph of trees
Preparation
comment = r'\#.*'
symbol = r'\w+'symbol_enumeration = symbol
("," symbol)*float = r'\d+\.\d+'integer = r'\d+'string = '"' r'[^"]*' '"'interval = symbol ".." symbolbrackets = "[" symbol "]"
...
Preparation by Etalab and DGFiP :● understand the Domain Specific
Language (DSL) : M● parse using Clean PEG (Igor
Dejanović's Arpeggio)● simplify the Abstract Syntax Tree
(AST)
→ Direct Acyclic Graph of trees
Preparation
Python object / JSON
● Directed Acyclic Graph (DAG) traversal (400ms)
● Arithmetic computations at each node (0.4ms in total for a single simulation)
During the hackathonEfficient computation
vs400ms + 0.4ms = 400.4ms
for 1 simulation
400ms + 10.000x0.4ms = 4.4s
for 10.000 simulation
Long live Numpy and vectorized computations !
During the hackathonVisualise
During the hackathonSimplify the graph for common fiscal situations
During the hackathonTranspile to other languages
var functionsMapping = {
'+':function sumTab(tabValeurs){ return tabValeurs.reduce(function(a,b){ return a+b; }); },
'*':function mulTab(tabValeurs){ return tabValeurs.reduce(function(a,b){ return a*b; }); },
. . .
Step 1 : Define an implementation of the operations
During the hackathonTranspile to other languages
function computeFormula(node, values){ if(node.nodetype ==='symbol'){ var value = values[node.name]; if(typeof(value)==='undefined'){ value = 0; }; return value }else if(node.nodetype ==='float'){ return node.value; }else if(node.nodetype==='call'){ var name = node.name; var func = functionsMapping[name]; var args = []; for(i in node.args){ args.push(computeFormula(node.args[i],values)); } return func(args); }}
Step 2 : Code a DAG traversal
III – From code to data
II – The French tax calculator
Tax rules vs implementation
Rule of least power
different concerns
storageversioning
editing
speedsimplicity
(technologies evolve fast)
Python Code Quality Authority
Parsing the current code
Baron
Redbaron
Astroid Custom pythonpython → julia
2to3
The future
Tax rules written in
DSL(s)
Unique internal graph
representation
Implementation(s)
The glue ? Python ? A functional language ?
Take-away message
Language choice is not definitive !(if you start with python)
Thank you !
http://www.openfisca.fr/https://framagit.org/openfiscahttps://github.com/openfisca
@OpenFisca
Michel [email protected]
PyData – June 14, 2016
We are hiring !
