Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Increasing market efficiency: Evolution of cross-correlations of stock
  returns   We analyse the temporal changes in the cross correlations of returns on the
New York Stock Exchange. We show that lead-lag relationships between daily
returns of stocks vanished in less than twenty years. We have found that even
for high frequency data the asymmetry of time dependent cross-correlation
functions has a decreasing tendency, the position of their peaks are shifted
towards the origin while these peaks become sharper and higher, resulting in a
diminution of the Epps effect. All these findings indicate that the market
becomes increasingly efficient.

25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex