The links provided above mention this, but it should be emphasized how bad this effect is.
http://www.cbpp.org/1-13-05sfp3.htm--snip
The “Ratchet Effect”: Increasing the Severity of the Population-plus-Inflation Formula
Colorado’s TABOR and many current TEL proposals in other states contain a feature that causes public services to be cut even more than they would under a simple population-growth-plus-inflation formula. This feature is known as the “ratchet effect.” With the ratchet effect, the population growth plus inflation adjustment is applied to the amount of actual expenditures or revenue in the prior year (rather than to the amount of allowable expenditures or revenues). When state budgets grow slowly or fall, as in the recent fiscal crisis, actual spending or revenues are likely to be lower than the level permitted by the formula. If this lower level becomes the new base to which the population growth and inflation adjustment is applied, then the level of public services is permanently ratcheted down.
Consider a hypothetical state with $1 billion in revenues in 2001 and with population growth plus inflation equaling 5 percent annually. With no ratchet effect, by 2005 allowable revenue would be $1.22 billion (reflecting four years of 5 percent growth, compounded). But if actual revenue collections declined in the first year by 5 percent, allowable revenue collections in years thereafter would be calculated from that new, lower base. As a result, by 2005, even if the economy and tax base fully recovered, allowable revenues could not exceed $1.1 billion — a very significant difference of 10 percent.
The ratchet effect typically is not explicit, but rather hidden within the wording of a TABOR proposal. Any TABOR proposal must be carefully scrutinized to determine whether it contains a ratchet effect.