Table:
Pension

2019	2018	2017

Net periodic benefit cost:

Expected long-term return on plan assets(1)	3.6%	3.8%	3.3%

Rate of compensation increase	4.4%	3.3%	2.7%

Discount rate	2.2%	2.1%	1.9%

Projected benefit obligation:

Expected long-term return on plan assets	2.0%	3.6%	4.0%

Rate of compensation increase	4.3%	4.4%	4.4%

Discount rate(2)	1.7%	2.2%	2.3%

Answer the following question using the table plus the background text, produce your answer and, if helpful, briefly explain your calculation. Conclude with JSON: {"answer": ["ANSWER"], "scale": "SCALE"} ("scale" = "" if no unit).

Text:
Assumptions
Weighted-average actuarial assumptions used to determine net periodic benefit cost and projected benefit obligation for the plans for the fiscal years 2019, 2018 and 2017 were as follows:
(1) The expected return on plan assets assumption used in calculating net periodic benefit cost is based on historical return experience and estimates of future long-term performance with consideration to the expected investment mix of the plan.
(2) The discount rate is used to state expected cash flows relating to future benefits at a present value on the measurement date. This rate represents the market rate for high-quality fixed income investments whose timing would match the cash outflow of retirement benefits. Other assumptions include demographic factors such as retirement, mortality and turnover.

Question: What was the percentage change in the projected benefit obligation discount rate between 2018 and 2019?

1.7-2.2, therefore {"answer": "-0.5", "scale": "percent"}