This may be because the duration of research is the issue of economic and political issues within the country and the world economy, thus making these values with uncertainty occurs.
This could be due to a period of research into the problems of economic and political problems in the country and engage with the global economy, the value of these uncertainties occur.
This may be due to a period of this research is that economic problems and political issues within and along with world economic situation the parameters. These little uncertainty occurs.