(1) Beginning on July 1, 2007, the assessment rate for vinifera grapes grown in this state shall not be less than three dollars per ton nor more than twelve dollars per ton. The assessment rate for wine producers shall not be less than $0.02 per gallon nor more than $0.08 per gallon. The Washington wine commission may adjust the assessment amount levied on wine producers and grape growers as needed to fund necessary commission activities. Provided, that any adjustment in the assessment rate by the commission be levied in an equal and proportional manner upon both the wine producers and grape growers. In determining whether to adjust the assessment amount the commission shall consider the following factors:

(a) The commission's budgetary needs, including but not limited to a qualitative and quantitative review of programs carried out in the preceding year by the commission. This review should consider whether the program met its goals, benchmarks and objectives and whether the program constitutes the best use of the wine commission's finite resources;

(b) Projected grape production;

(c) Changes in administrative costs;

(d) Changes in the industry outside the control of the wine commission.

(2) The commission shall provide grape growers and wine producers notice of changes in assessment rates in a timely and reasonable manner and in no instance shall the notice be less than thirty days from the date the assessment is due.