We're pricing a 5-year commercial loan and need to use a PD. Should we use a Point-in-Time (PIT) PD or a Through-the-Cycle (TTC) PD? How do they differ, and what happens to both if we enter a sudden recession?

我们在给一笔5年期的商业贷款定价，需要用到PD。你认为应该用时点型（PIT）PD还是跨周期（TTC）PD？如果突然爆发经济衰退，这两种PD会发生什么变化？