Interpret the highlighted in yellow horizontal analysis trend.

	2020	2019	2018	2017	2016
ASSETS
Property, plant and equipment	28.37%	19.98%	16.29%	8.83%	100.00%
Accumulated depreciation	18.98%	15.05%	16.79%	10.24%	100.00%
Property, plant and equipment, net	31.47%	21.61%	16.12%	8.36%	100.00%
Current assets:
Cash and cash equivalents	629.33%	-20.00%	73.33%	-26.67%	100.00%
Accounts receivable, net of allowance for					100.00%
uncollectible accounts.	19.33%	9.29%	11.90%	1.12%	100.00%
Unbilled revenues	-21.67%	-34.60%	-29.28%	-19.39%	100.00%
Materials and supplies	20.51%	12.82%	5.13%	5.13%	100.00%
Total assets	34.00%	22.72%	14.83%	5.41%	100.00%