1. What is a CapEx cycle? 2. Why nominal GDP is an important variable for debt sustainability analysis?

In yesterday’s paper, I read an interview on fiscal policy and budget of the government. The interview mentioned capex cycle. What is that?

Moreover, the interviewee, an Economics Professor, said, “nominal (GDP) growth is a very important variable in any debt sustainability analysis – how much capacity you have to pay off your debt over time.” Why so?