Pivot Table Help

[whynot]

i created a pivot table using data i downloaded from a government website.
The pivot table accurately calculates the average price per quarter.
However, when i try to calculate the year over year change in the pivot table is does not display data for the first quarter and does not provide an accurate calculation.
in order to calculate the year over year change i created a second column for price within the pivot table, i used show value as and selected % difference from, i selected base field as Date(quarter), and base item as previous.

I am using office 365.

i truly appreciate the help. Have been struggling a few hours with this.

Book1
	A	B	C
3	Row Labels	Average of Price	Year Over Year Change
4	1990
5	Qtr3	$1.24
6	Qtr4	$1.33	6.97%
7	1991
8	Qtr1	$1.09
9	Qtr2	$1.11	1.63%
10	Qtr3	$1.11	-0.14%
11	Qtr4	$1.09	-1.73%
12	1992
13	Qtr1	$1.01
14	Qtr2	$1.10	8.99%
15	Qtr3	$1.13	1.96%
16	Qtr4	$1.10	-2.18%
17	1993
18	Qtr1	$1.06
19	Qtr2	$1.09	3.48%
20	Qtr3	$1.06	-2.72%
21	Qtr4	$1.06	-0.45%
22	1994
23	Qtr1	$1.00
24	Qtr2	$1.05	4.59%
25	Qtr3	$1.14	8.16%
26	Qtr4	$1.11	-2.57%
27	1995
28	Qtr1	$1.08
29	Qtr2	$1.16	7.98%
30	Qtr3	$1.13	-2.64%
31	Qtr4	$1.07	-5.00%
32	1996
33	Qtr1	$1.10
34	Qtr2	$1.25	13.53%
35	Qtr3	$1.21	-3.30%
36	Qtr4	$1.22	1.01%
37	1997
38	Qtr1	$1.22
39	Qtr2	$1.20	-1.92%
40	Qtr3	$1.21	1.05%
41	Qtr4	$1.16	-3.94%
42	1998
43	Qtr1	$1.05
44	Qtr2	$1.05	0.53%
45	Qtr3	$1.03	-2.26%
46	Qtr4	$0.99	-4.15%
47	1999
48	Qtr1	$0.95
49	Qtr2	$1.13	18.51%
50	Qtr3	$1.21	7.67%
51	Qtr4	$1.26	3.60%
Gas Prices - Pivot Table 2