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Trading on Algos
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Johannes A. Skjeltorp
Norges Bank
Elvira Sojli
Erasmus University Rotterdam
Wing Wah Tham
Erasmus University Rotterdam and Tinbergen Institute
Preliminary Draft
Comments welcome
Abstract
This paper studies the impact of algorithmic trading (AT) on asset prices. We nd
that the heterogeneity of algorithmic traders across stocks generates predictable patterns
in stock returns. A trading strategy that exploits the AT return predictability generates
a monthly risk-adjusted performance between 50-130 basis points for the period 1999
to 2012. We nd that stocks with lower AT have higher returns, after controlling for
standard market-, size-, book-to-market-, momentum, and liquidity risk factors. This
eect survives the inclusion of many cross-sectional return predictors and is statistically
and economically signicant. Return predictability is stronger among stocks with higher
impediments to trade and higher predatory/opportunistic algorithmic traders. Our paper
is the rst to study and establish a strong link between algorithmic trading and asset
prices.
http://www2.warwick.ac.uk/fac/soc/wbs/subjects/finance/fof2014/programme/elvira_sojli.pdf
Table 3
Algorithmic trading and stock returns: Uni-variate comparisons
The table shows the average monthly returns for stocks cross-sorted by AT and dierent characteristics. Each
month t we divide the sample in terciles based on end of month characteristic (size, book-to-market, relative
spread, trading volume in USD, past month returns, and past 12 month return). Within each characteristic we
sort stocks into ve AT portfolios, where the AT1 portfolio contains stocks with the lowest AT and AT5 stocks
with the highest AT. We then compute the equal-weighted average return over for month t + 1 for the ve AT
portfolios within each characteristic and the return dierence between the low and high AT portfolios. All
returns are calculated using bid-ask midpoint prices (adjusted for splits and cash distributions) and corrected
for delisting bias, -30% return for stocks with delisting codes 500 and 520-584. t-stat shows the t-statistic for
the dierence in returns test for AT1-AT5.
Average monthly (%) returns (t+1
AT (t)
AT1 AT2 AT3 AT4 AT5 AT1-AT5 t-stat
Panel A: by MCAP
Low MCAP 2.67 2.17 1.67 1.39 1.21 1.46 5.20
Med MCAP 1.39 1.03 0.69 0.86 0.66 0.73 1.46
High MCAP 0.55 0.42 0.63 0.54 0.57 -0.01 -0.03
Panel B: by BM
Low BM 1.06 0.89 0.68 0.63 0.61 0.44 0.95
Med BM 1.54 1.17 0.81 0.79 0.74 0.80 2.20
High BM 1.96 1.74 1.34 1.38 1.02 0.94 3.40
Panel C: by SPREAD
Low SPREAD 0.76 0.72 0.77 0.68 0.44 0.31 0.67
Med SPREAD 1.69 1.25 0.77 0.65 0.67 1.03 2.49
High SPREAD 2.58 1.98 1.24 1.26 0.81 1.76 6.04
Panel D: by USDVOL
Low USDVOL 2.44 1.91 1.33 1.25 0.86 1.58 7.28
Med USDVOL 2.08 1.27 0.83 0.93 0.72 1.36 3.09
High USDVOL 0.61 0.64 0.59 0.61 0.43 0.19 0.35
Panel E: by R1
Low R1 1.36 1.30 0.94 0.91 0.86 0.49 1.15
Med R1 1.51 1.14 0.98 0.94 0.68 0.83 2.77
High R1 1.51 1.19 1.00 0.89 1.11 0.40 1.09
Panel F: by R212
Low R212 1.59 1.48 1.02 0.99 0.80 0.79 2.09
Med R212 1.30 0.99 0.84 0.87 0.82 0.47 1.85
High R212 1.36 1.35 1.14 0.97 1.16 0.20 0.46
UQ