TO prevent the most drastic cuts required by Washington's state budget shortfall this year, Gov. Chris Gregoire has proposed a time-limited, half-cent increase in the sales tax. Most agree that the fairest way to raise revenue is through a progressive income tax, but that's not what's on the table. Even so, many are reluctant to support a sales-tax increase, seeing it as regressive. But is it?

What makes a tax "regressive"?

Technically, it's regressive if the tax burden decreases as income increases — if the rich pay less as a portion of their incomes than the poor. Take the example of a purchase. If someone with an annual income of $20,000 buys a car for $5,000, and pays a 10 percent sales tax of $500, that tax takes 2.5 percent of their income. But if someone with an income of $50,000 makes the same purchase, their tax is only 1 percent of their income. And for those with incomes of $100,000, the tax represents even less — a mere one-half of 1 percent of their income. So, as a proportion of income, the low-income buyer pays five times as much in taxes as the high income buyer.

This approach, however, asks the wrong question. A better way is to ask: How much of what lower-income households spend is subject to sales tax? The answer is "not as much as one would think, and less than the rich." We know this from the Self-Sufficiency Standard, a measure of the minimum income required to meet one's basic needs at a "bare bones" budget level (e.g., the food part of this budget includes no takeout or restaurant food, no pizzas or lattes).

The essentials, which make up most of this budget — housing, groceries, child care, transportation and health care — are not subject to the sales tax. Only "miscellaneous" — clothes, household items, gifts, etc. — is subject to sales tax, and "miscellaneous" is only 10 percent of the total.

Of course, real people do spend on more than the basics, even at low incomes. But low-income families spend much more of their incomes on these basics than do higher-income families. According to the 2010 Consumer Expenditure Survey (CES), for households with incomes in the bottom one-fifth, nearly two-thirds (62 percent) of their spending was on four core items: housing/utilities, food, transportation and health care. Those in the middle spent 55 percent for these core items, and those in the top one-fifth spent only 45 percent. If you deduct other items, such as contributions and education (also not subject to the sales tax), only 29 percent (or less) of expenditures of those at the bottom are subject to the sales tax.

This analysis does not take into account large, one-time purchases, such as a car. One way to address this issue is to exempt low-income consumers making a necessary purchase, such as a car needed for work, as is done with property taxes.

In addition, the amount of money involved is small, especially for low-income families. Assuming that the maximum 29 percent of average spending of the bottom quintile is subject to the sales tax, a half-cent increase would amount to just 58 cents more per week at the most, but about $2.82 more per week for the richest one-fifth.

So while the sales tax is "regressive" — low-income people do pay a higher percentage of their income in taxes than high-income people — it is not as bad as it first appears.

And, when balanced against the impact of the proposed cuts on low-income families — fewer school days, ending Basic Health coverage, increasing hunger and homelessness — raising the sales tax by half a cent is the better choice.