March 7th, 2010, 9:33 pm
Reuters provides a consolidated tick feed from all exchanges, major and obscure - be it NYSE or Karachi. However: - The feeds are "real time", but not very low latency. Moreover, for most of European stock exchanges and even US futures exchanges all ticks are time stamped with low resolution. Not 1 millisecond, but 1 second, if not worse. So, latency does not really matter for them. Of course, for many developing countries latency does matter in principle - what milliseconds, if not all of these excahnges even trade continuously.- The Reuters data are not very clean - my guess it that Reuters just sends what it receives from sources. - Reuters does not normalize data, that makes it difficult to work with them. Particularly: -- What fields are supplied for ticks, as well as the number and format of the fields depends on country and/or on exchange-- Trade volumes are reported different way by different exchanges : usually per trade, but sometimes cumulative for the day from market open -- Some exchanges report two-side quotes (buy and sell), other one-side quotes, other a mix-- A trade often is reported on the same tick with a quote-- The data formats change time to time, per exchange-- Reuters not enforces its specifications. For example, per specification not more than N fields can be supplies for a single tick, but if one of exchanges decides to send N+1 fields, Reuters passes them to users. Depending on how user's codes were designed, it is not absolutely unusual if the codes crash or corrupt data when it happens.Even if you know where to look, sorting out the irregularities would require may be 12 man x months, hardly less than 6. However, it can be done much faster if you limit yourself to may be 20 major exchanges and do not care about Bogota and Colombo.I do not know who is selling historical ticks data for all major exchanges. NYSE is selling TAQ dataset of ticks for US cash instruments.