In accordance withthe experience, the paper discusses thetrouble reason and its solution to the PC-20X30 numerical plasmacutterin detail, andthen introduces the maintenanceflow chart.
The trouble is that this centres the fan chart on the mode of the distribution (the single likeliest outcome), and not necessarily on the median (the value that divides the outcomes, ranked by size, exactly in two) or the mean (the sum of the outcomes divided by the number of outcomes).
Government debt has soared since the start of the decade, creating a potential source of trouble when the next recession hits tax revenues (see chart).