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help for apch
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Generalized linear models for age-period-cohort effects with hysteresis

    Syntax

        apch depvar [indepvars] [if exp] [in range] [weight] , [ age(string)
              period(string) glm_options ]

    apch allows all varlists & weights that glm considers.


Description

apch estimates age-period-cohort APC-D (detrended) models and provides
detrended (0 sum and 0 slope) parameters of age, period and cohort effects;
appropriate constraints offer a unique solution & solve the traditional APC
identification problem.  We focus on cohort parameters (DCE=detrended cohort
effect) that should be tested to be non-zeros across cohort span.  Their
"hysteresis" (durability) over life course is assessed & tested by a
coefficient h (hysteresis) that is 0 in case of linear stability of cohort
effect, -1 in case of vanishing of the cohort effect over life span, equal to 1
in case of development from 0 of the cohort effect over life course.  Since the
cohort parameters and the hysteresis parameter can not be assessed
simultaneously, the package proposes an iterative strategy that converges to a
single stable solution.  The apch provides Raftery's bics able to assess the
interest of cohort effect and then of hysteresis effect.

The user provides a dependant variable, age and period, and controls from a mic
> rodata 
series of crossectional surveys. 
The data must be a complete rectangle (age x period) and the pace between perio
> ds must 
be fix and equal to the distance between age groups. If not, the procedure will
>  fail.  

The procedure delivers :
(1) An APC-Detrended model with controls, including zero-sum/zero-slope paramet
> ers of 
        age, period & cohort effects.
(2) An APC-Hysteresis model with controls, delivering the h-hysteresis paramete
> r of 
        linear stability of the DCE. 
(3) Delta BICs are provided to measure 
        (a) dbic_cohort : the interest of including cohort effects after a AP m
> odel and 
        (b) dbic_hyster : the interest of including hysteresis effects to the A
> PC model 


Options

age(string) and period(string) specify the names of age and period variables.
    They must be given by the user.

Any glm_options can be valid options for apch.

Many types of model can be handled by apch :

* the user must call "family(bin) link(logit)" for a logit regression

* the user must call "family(poisson) link(log) exposure(pop)", where pop is
the population at risk, for a poisson model

* the default "family(gauss) link(id)" will provide a linear regression.


Since apch makes use of complex constraints, this package should be processed
on STATA 11.0 or higher.

example

use "http://www.louischauvel.org/apchexb.dta", clear

apch mf2 , age(age) period(year)

References

see http://www.louischauvel.org/apchex.htm for working paper and examples on
    apch.

see Yang, Y., Fu, W., and Land, K. 2006. apc_ie and apc_cglm STATA packages.

Author

Louis Chauvel
Sciences Po Paris
During the completion of the v1.0
Louis Chauvel was also invited Pr at Columbia U 
Dpt of sociology, Knox Hall
chauvel@louischauvel.org

Also see

Online: help for glm.