Large-Scale Allocation of Personalized Incentives Lucas Javaudin1 Andrea Araldo2 André de Palma1 1CY Cergy University lucas.javaudincyu.fr andre.de-palma.cyu.fr

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Large-Scale Allocation of Personalized Incentives
Lucas Javaudin1, Andrea Araldo2, André de Palma1
1CY Cergy University; lucas.javaudin@cyu.fr; andre.de-palma.cyu.fr
2Télécom SudParis, Institut Polytechnique de Paris; andrea.araldo@telecom-sudparis.eu
Abstract—We consider a regulator willing to drive individual
choices towards increasing social welfare by providing incentives
to a large population of individuals.
For that purpose, we formalize and solve the problem of
finding an optimal personalized-incentive policy: optimal in the
sense that it maximizes social welfare under an incentive budget
constraint, personalized in the sense that the incentives proposed
depend on the alternatives available to each individual, as well as
her preferences. We propose a polynomial time approximation
algorithm that computes a policy within few seconds and we
analytically prove that it is boundedly close to the optimum. We
then extend the problem to efficiently calculate the Maximum
Social Welfare Curve, which gives the maximum social welfare
achievable for a range of incentive budgets (not just one value).
This curve is a valuable practical tool for the regulator to
determine the right incentive budget to invest.
Finally, we simulate a large-scale application to mode choice
in a French department (about 200 thousands individuals) and
illustrate the effectiveness of the proposed personalized-incentive
policy in reducing CO2emissions.
I. INTRODUCTION
Taxes and subsidies in transportation are often perceived
by the population as unfair, since they neglect the alternatives
actually available to each individual and the individual pref-
erences. On the other hand, with the increase in information
available to governments [1], economic policies can be im-
proved to consider the peculiarities of each individual. We pro-
pose a policy of personalized incentives in a framework where
individuals choose between multiple alternatives options. A
regulator has a limited budget that he can use to propose
monetary incentives, with the goal to induce individuals to
change their choice toward socially-better ones. Most incentive
policies in the literature are not personalized [2], [3], with
some exception [4]. Differently from the latter, we seek for a
method with provable performance bounds.
We define the optimal personalized-incentive policy as the
allocation of incentives that maximizes social welfare (defined
as the reduction of CO2emissions in the example above),
for a given budget. We formalize the problem of finding a
personalized-incentive policy maximizing social welfare under
the regulator’s budget constraint and show that it reduces to
the well-known Multiple-Choice Knapsack Problem (MCKP
– §II), which has been used in several contexts, like Eco-
nomics [5] and Computer Science [6]. To approximate the
optimal policy in polynomial time, we adapt a greedy algo-
rithm from the Operations Research literature and we analyze
some of its analytical (e.g., suboptimality gap bound) and
economic (e.g., diminishing returns) properties (§III). While in
most of the paper we assume that the regulator knows exactly
the preferences of each individual, we also study the case of
imperfect information (§IV).
Using data from the French census at the scale of a
French department, we evaluate the CO2reduction achieved
via the transportation mode incentive policy computed with
our algorithm (§ V). The results show that our personalized
incentives achieve the same CO2reduction as flat subsidies,
but with a considerably smaller amount of incentives spent.
Our code is available as open source [7].
We are aware that our framework is based on several
idealized assumptions that makes its direct applicability dif-
ficult in practical situations, in particular for what concerns
the assumption of being able to collect precise information
about individual preferences. In this sense, the path toward
personalized-incentives is still a long way to go. However, we
argue that the theoretical findings of this paper, coupled with
the continuous evolution of techniques for collecting societal
big-data, while respecting privacy, provide important steps
along this path.
II. FRAMEWORK AND INCENTIVE POLICY
A. Model
We consider a population I ≡ {1, . . . , m}of mindi-
viduals. Each individual i I chooses an alternative j
among an individual-specific choice-set Ni. For example,
we can consider individuals choosing a mode of transporta-
tion to commute to their work. In this case, the choice
set could be Ni={car,walk,bike,public transit}. The
choice set can be individual-specific so that if individ-
ual iowns a car but individual i0does not, we could
have Ni={car,walk,bike,public transit}and Ni0=
{walk,bike,public transit}.
Let yi,j >0be an incentive provided by the regulator to
individual i, when she chooses alternative j. Since yi,j changes
from an individual to another, such policy is personalized.
A policy influences the individual choice since the proposed
monetary transfers change her utilities. The utility Ui,j of
individual iwhen choosing alternative j∈ Niis given by
Ui,j =Vi,j +yi,j ,, where Vi,j Ris the intrinsic utility
(in the absence of policy). Each individual ichooses an
alternative j
iwhich maximizes her utility j
iarg maxjUi,j .
Each alternative jof individual iis characterized by a social
indicator bi,j R(e.g., the opposite of CO2emissions
induced by the commutes).
We assume the regulator has perfect information: it knows
exactly the intrinsic utilities {Vi,j }i,j and social indicators
1
arXiv:2210.00463v1 [econ.EM] 2 Oct 2022
{bi,j }i,j of all the alternatives, for all the individuals. We will
relax this assumption in §IV.
The alternative chosen by each individual iin the absence of
policy (i.e., where yi,j = 0,i, j) is called default alternative,
and denoted j0
i,arg maxj0arg maxjVi,j bi,j0. In order to
convince an individual ito shift from its default alternative
to any other alternative j, it is necessary and sufficient for
the regulator to provide an incentive wi,j ,Vi,j0
iVi,j , to
compensation for the decrease of individual utility.
B. Maximum Social Welfare Problem
The regulator has to decide, for each individual i, which al-
ternative to incentivize, which can be summarized by a binary
decision variable xi,j that is equal to 1if the regulator wants
to make individual ichoose alternative j, and 0otherwise.
The incentive can be thus written as yi,j =xi,j ·wi,j . The
Maximum Social Welfare problem is
max
{xi,j }i,j X
i∈I X
j∈Ni
bi,j xi,j (1)
s.t. X
i∈I X
j∈Ni
wi,j xi,j Q(2)
X
j∈Ni
xi,j = 1, i ∈ I (3)
xi,j ∈ {0,1}, i ∈ I, j ∈ Ni(4)
The objective function (1) aims to maximize the social welfare,
i.e., the sum of all social indicators, constraint (2) indicates
that the regulator cannot spend more than Q. Moreover, only
one alternative per individual is incentivized (3).
For any budget Q, we indicate with B(Q)the maximum
of the social welfare, solution of problem (1).
C. Maximum Social Welfare Curve Problem
Suppose now that the regulator is endowed with a maximum
budget Qand that he can spend any budget in the interval
Y[0, Q]. To decide the exact amount of budget that is
convenient to spend, it is useful to obtain the Maximum Social
Welfare Curve C
Q, representing the maximum social welfare
reachable, B(Y), for any budget Y[0, Q], i.e. C
Q=
{(Y, B(Y)) |Y[0, Q]}, which is clearly monotone non-
decreasing (the larger the budget spent, the larger the social
welfare reached). Observe that, although a maximum budget
Qis available, the regulator may not want to indiscriminately
spend it all, but may choose the actual budget to invest in
incentives, based on several criteria. For instance, the regulator
may use the above curve to find the minimum budget needed
to reach a certain social-welfare target (see the example of
Fig. 3).
III. APPROXIMATION ALGORITHM
The MCKP problem, and thus the Maximum Social Welfare
problem (1), is NP-hard [8] . We provide in this section a
polynomial time algorithm based on greedy algorithms from
the Operations Research literature, which gives us solutions
boundedly close to the optimum.
A. Preliminary Steps
Before presenting the proposed algorithm, we need to
“clean” the input of the problem, removing some irrelevant
alternatives from the set Niof the alternatives of any individ-
ual i[8, Section 11.2.1]. In broad terms, irrelevant alternatives
are the ones that do not provide enough social indicator
compared to the incentive amount needed to induce them. The
alternatives remaining after the cleaning are usually called LP-
extremes and we denote them with Ri⊆ Ni. Figure 1 gives the
intuition behind the process of constructing the set Ri, which
is called concavization [9, Fig.1,2]. In the figure, alternative
3is irrelevant since 2provides a larger social indicator, while
requiring less incentive. Alternative 7is irrelevant since it
requires to spend more incentive than 6, for a negligible
gain in the social indicator. It is much more convenient to
make a slightly bigger investment to induce alternative 9,
which provides a significant social indicator improvement with
respect to 6.
Fig. 1: Alternative set Niof individual iand the subset Riof
LP-extremes.
We follow the Operations Research literature in the slight
abuse of notation of denoting with wi,j the incentive to be
provided to the j-th alternative in Ri. With no loss of gener-
ality, we can assume the ordering wi,1< wi,2<··· < wi,|Ri|.
Obviously, the default alternative is the first alternative in the
set Riand wi,1= 0.
Definition III-A.1 (Efficiency and incremental efficiency).We
define the efficiency of an alternative jof individual ias ei,j ,
bi,j bi,j0
i
wi,j , i.e., the gain in social indicator that we can gain
via a unit of incentive allocated to that alternative.
We also define the incremental social indicator ˜
bi,j and the
incremental incentive ˜wi,j required for each alternative j
Rias
˜
bi,j ,bi,j bi,j1
˜wi,j ,wi,j wi,j1
, j = 2,...,|Ri|.(5)
The incremental efficiency is then defined as ˜ei,j ,˜
bi,j /˜wi,j .
The incremental efficiency ˜ei,j can be interpreted as the
increase in social welfare for each monetary unit spent, when
individual ishifts from alternative j1to alternative j.
2
摘要:

Large-ScaleAllocationofPersonalizedIncentivesLucasJavaudin1,AndreaAraldo2,AndrédePalma11CYCergyUniversity;lucas.javaudin@cyu.fr;andre.de-palma.cyu.fr2TélécomSudParis,InstitutPolytechniquedeParis;andrea.araldo@telecom-sudparis.euAbstract—Weconsideraregulatorwillingtodriveindividualchoicestowardsincre...

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