Understanding the Lagrangian Function for Maximization Problems

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Discussion Overview

The discussion revolves around understanding the Lagrangian function in the context of a maximization problem presented in an economics paper. Participants are attempting to clarify the process of deriving the first-order conditions (FOC) with respect to a specific variable, r(y,α), using calculus rules.

Discussion Character

  • Technical explanation
  • Homework-related
  • Debate/contested

Main Points Raised

  • One participant presents a complex Lagrangian function and seeks help in deriving the first derivative with respect to r(y,α), suggesting the use of Leibniz's rule and the chain rule.
  • Other participants express confusion regarding the clarity and completeness of the initial problem statement, indicating that more information is needed to understand the context and notation used.
  • Clarifications are requested regarding the definitions of terms and the specific problem being addressed, with a suggestion to provide a reference to the original paper for better understanding.
  • A later reply reiterates the need for additional information and context, emphasizing the importance of defining all notation used in the discussion.

Areas of Agreement / Disagreement

Participants generally agree that the initial post lacks sufficient detail for a meaningful discussion. There is no consensus on how to proceed with the derivation due to the unclear presentation of the problem.

Contextual Notes

Limitations include the absence of definitions for the notation used in the Lagrangian function and the specific problem context, which may hinder understanding and the ability to derive the requested first-order conditions.

arfie
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Hi everyone!

I really need help for this. I have to read a paper in economics where some parts I don't understand.

Suppose:

S \equiv [\alpha,\bar{\alpha}]x[y,\bar{y}]
V^e(p_j,g_j,y+r(r\alpha)-T_j,\alpha)\equiv \underset{h}{\text{max}}U(y+r(r,\alpha)-T_j,p_jh,h,g_j;\alpha)

And then from maximization problem I have a Lagrangian function as follows:

L=<br /> \sum_{i = 1}^{J} \Big[\int_S \omega (y,\alpha) V^e(p_i,y+r(y,\alpha)-T_i,g_i,\alpha) a_i(y,\alpha)f(y,\alpha)\,dy\,d\alpha<br /> + \omega_R(R/J+\int_0^{p_i/(1+t_i)}H^i_s(z)\,dz)\Big]

\lambda_1[R+\int_S r(y,\alpha)f(y,\alpha)\,dy\,d\alpha]+\lambda_2[\int_S h_d(p_i,y+r(y,\alpha)-T_i,g_i,\alpha)a_i(y,\alpha)f(y,\alpha)\,dy\,d \alpha-H_S^i]

How can I solve for FOC for the lagrangian function with respect to r(y,\alpha)? What rules should I use? I guess it has something to do with Leibniz's rule and chain rule but I'm not sure. Thanks!
 
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Definitely not enough info here for anyone to understand what's going on. For instance, "solve for FOC for the lagrangian function with respect to r(y,a)" is meaningless to me.
 
joeblow said:
Definitely not enough info here for anyone to understand what's going on. For instance, "solve for FOC for the lagrangian function with respect to r(y,a)" is meaningless to me.

Thanks for the reply.
I mean "how to get first derivative of L w.r.t r(y,a) which is dL/dr(y,a)?"
 
arfie said:
Thanks for the reply.
I mean "how to get first derivative of L w.r.t r(y,a) which is dL/dr(y,a)?"

Sorry, but you're going to have to give way more information. Start by defining all the notation you use. Describe the actual problem that's given. Maybe give a reference to where you have seen this.
 
micromass said:
Sorry, but you're going to have to give way more information. Start by defining all the notation you use. Describe the actual problem that's given. Maybe give a reference to where you have seen this.

Sorry if it's not that clear. The reference is here: http://www.nber.org/papers/w17251.pdf
My problem is in page 14, equation (20). I don't know how to get it.
 

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