be defined. Following the classical stochastic pro-
gramming framework (Birge and Louveaux, 2013;
Ruszczy
ˇ
nski and Shapiro, 2003), uncertain parame-
ters can be dealt as random variables defined on a
given probability space and under the assumption of
discrete distribution, they can be represented in terms
of scenarios, each occurring with a given probability
value. A scenario based approach for the IT problem
was proposed by (Consiglio and Zenios, 2001) where
the tracking error is represented in terms of the MAD.
More recently, (Beraldi and Bruni, 2018) addressed
the IT problem by the chance constrained paradigm
(both in the basic and integrated form). Both the back-
ward and the forward perspectives described so far are
defined in a static setting. Once selected, the portfolio
is not rebalanced during the considered time horizon
in the hope that the future behaviour will be close to
the desired one. In a dynamic setting, the portfolio
composition can be revised from time to time accord-
ing to new market information, if the tracking accu-
racy starts to deteriorate. Dynamic index tracking has
been mainly addressed in a deterministic setting. For
example, in (Gaivoronski et al., 2005) the authors pro-
posed several dynamic formulations differing for the
adopted tracking measures. Very recently, Strub and
Baumann addressed in (Strub and Baumann, 2018)
the problem of the optimal construction and rebalanc-
ing of index tracking portfolios. They proposed and
compared different deterministic formulations for re-
balancing that are iteratively solved within a rolling
horizon scheme. A multi-objective evolutionary al-
gorithm has been proposed in (Chiam et al., 2013)
and applied for both the single-period and the multi-
period index tracking problem.
When the dynamic and the stochastic elements are
jointly addressed, the problem becomes even more
challenging. However, only a few number of contri-
butions deal with this more involved case. A two-
stage stochastic programming formulation has been
proposed in (Stoyan and Kwon, 2010). The model
aims at minimizing the MAD risk measure and in-
cludes some real features. The multi-stage paradigm
has been adopted in (Barro and Canestrelli, 2009),
where the authors focus on tracking error measures
and consider as objective function the weighted sum
of a first term accounting for the deviation from the
benchmark and a second penalty term accounting for
the portfolio turnover. Local volatility and tail risk are
both controlled in the stochastic formulation proposed
in (Barro et al., 2018).
In this paper, we propose a multistage-stochastic
programming model where tracking accuracy is con-
trolled by the Conditional Value at Risk (Rockafellar
and Uryasev, 2000). While the Value at Risk (VaR)
measures the maximum potential loss that can be ex-
perienced with a given confidence level, the CVaR al-
lows to control the tail risk, determining the expected
value of the losses exceeding the VaR. The relevance
of the CVaR is mainly related to the theoretical prop-
erties it satisfies. It is a “coherent” risk measure and
is consistent with the second degree stochastic dom-
inance. From a practical viewpoint, the CVaR is a
downside risk measure in the sense that it does not
penalize the deviations above a given target, typically
perceived as profit. Moreover, the CVaR is appealing
from a computational viewpoint since it admits, in the
case of discrete distributions, a linear programming
reformulation. When the CVaR is embedded within
a multistage model, the problem becomes more diffi-
cult to deal with since the time-consistency property
should be properly accounted for. Roughly speaking,
this property asserts that, at every state, optimality of
our decisions should not depend on scenarios that we
already know cannot happen in the future (de Mello
and Pagnoncelli, 2016). Starting from the stage-wise
risk measures properly defined, we build an aggre-
gated measure. It represents the first criteria to op-
timize together with the expected wealth. The con-
flicting nature of the two criteria is accounted by con-
sidering a bi-objective function where their relative
importance is weighted by the choice of a parameter
λ between [0, 1].
The rest of the paper is organized as follows. Sec-
tion 2 introduces the multistage stochastic program-
ming formulation. It is embedded into a rolling hori-
zon scheme, as detailed in Section 3. Section 4 reports
on the computational experiments carried out to eval-
uate the performance of the proposed strategy also on
the basis of an out of sample analysis. Conclusions an
future research directions are discussed in Section 5.
2 MODEL FORMULATION
We consider the problem of a fund manager who
wants to determine a portfolio that tracks a benchmark
(market index) over a given time horizon composed
of t ∈ T = {1, . . . , T } discrete time periods. Once ini-
tially composed, the portfolio can be rebalanced (by
buying and/or selling some assets) in response to new
market information.
We denote by {τ
t
}
t∈T
and {ξ
t
}
t∈T
, the random
evolution of the market index and the price of the dif-
ferent composing assets. Thus, for every t, ξ
t
is a
random vector of size |J|, where J denotes the set of
assets. Under the assumption of discrete random vari-
ables, the information structure can be described by
a scenario tree where, at each stage t ∈ T , there is a
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