Recent years have seen the dramatic growth of new modes of communication. Above and beyond using land line and mobile phone for voice real-time communication, people spend increasing amounts of time receiving and sending messages through social networks (e.g. Myspace or Facebook) and also...

An avalanche of articles has described the testing of a time series for the presence of unit roots. However, economic model builders have disagreed on the value of testing and how best to operationalise the tests. Sometimes the characterization of the series is an end in itself. More often, unit...