Odubel Herrera's Sudden Plate Discipline

Yesterday on the Fantasy Focus Baseball Podcast, Eric wondered whether any player has ever tripled his walk rate in consecutive (qualified) seasons.  This question was inspired by Odubel Herrera's astounding improvement in plate discipline this year.  He has increased his walk rate from 5.21% in 2015 to 14.55% in 2016 (a raw increase of 9.35%, or 2.79 times last year's rate).  I did some research using all qualified seasons since 1980 to find walk rate improvements.

In terms of raw increase in consecutive years, here are the leaders:

Rank	Player	Year 1	Year 2	Y1 BB%	Y2 BB%	Increase	Multiplier
1	Barry Bonds	2003	2004	26.91%	37.60%	10.69%	1.40
2	Odubel Herrera	2015	2016	5.21%	14.55%	9.34%	2.79
3	Mark McGwire	1997	1998	15.37%	23.79%	8.42%	1.55
4	Paul O'Neill	1993	1994	8.04%	16.25%	8.21%	2.02
5	Danny Tartabull	1991	1992	11.67%	19.58%	7.91%	1.68
6	Brian Giles	2001	2002	13.35%	20.96%	7.61%	1.57
7	Barry Bonds	2000	2001	19.28%	26.66%	7.38%	1.38
8	Von Hayes	1986	1987	10.72%	17.77%	7.04%	1.66
9	Gary Matthews	1980	1981	6.79%	13.79%	7.00%	2.03
10	Eric Chavez	2003	2004	9.48%	16.46%	6.98%	1.74

In terms of percentage increase (multiplier from year 1 to year 2), here are the leaders:

Rank	Player	Year 1	Year 2	Y1 BB%	Y2 BB%	Increase	Multiplier
1	Brian Hunter	1996	1997	3.07%	8.94%	5.87%	2.91
2	Alex Gonzalez	1999	2000	2.54%	7.28%	4.74%	2.87
3	Odubel Herrera	2015	2016	5.21%	14.55%	9.34%	2.79
4	Carlos Baerga	1994	1995	2.13%	5.83%	3.70%	2.74
5	Carlos Lee	1999	2000	2.51%	6.14%	3.63%	2.45
6	Ben Revere	2014	2015	2.08%	5.05%	2.97%	2.43
7	Adam Kennedy	2002	2003	3.73%	8.82%	5.09%	2.36
8	Ichiro Suzuki	2001	2002	4.07%	9.34%	5.28%	2.30
9	Alexei Ramirez	2008	2009	3.54%	8.09%	4.55%	2.29
10	Ozzie Guillen	1996	1997	1.89%	4.17%	2.28%	2.20

Hererra ranks 2nd in overall increase in walk rate (thanks to Barry Bonds, king of the intentional walk) and 3rd in percentage increase.  No player has tripled his walk rate in consecutive qualified seasons (since 1980), but the closest was Brian Hunter, who increased his rate from 3.07% in 1996 to 8.94% in 1997, a multiplier of 2.91.