percentage of highest certificate, diploma or degree of female lone parents and female parents in couples, aged 25 to 54 with children aged 15 and under in 1991, 2001 and 2011, canada
Table:
highest certificate, diploma or degree
female lone parents
female parent in couples

1991
2001
2011
difference
1991
2001
2011
difference

percent

total
100
100
100
..
100
100
100
..

no certificate, diploma or degree
34
20
13
-21
24
13
8
-16

high school diploma or equivalency
30
28
25
-5
32
28
21
-11

postsecondary certificate below the bachelor's level
26
39
42
16
29
36
38
9

university degree at the bachelor's level or above
9
13
20
11
15
23
33
18

Respond the following question with the most concise answer possible from the table. Return the answer in the JSON form {"answer": ["YOUR ANSWER"]}; for multiple items, use commas. The table is captioned 'percentage of highest certificate, diploma or degree of female lone parents and female parents in couples, aged 25 to 54 with children aged 15 and under in 1991, 2001 and 2011, canada'. Using the table, respond to this question: How much did the proportion of female lone parents that had a university degree increase from 1991 to 2011?

{"answer": ["difference"]}