Such sites track billions of dollars in contracts, subsidies and other state expenditures. All 50 offer so-called “checkbook level” spending details — those that identify each company from which goods and services are purchased. All but four let you search by recipient, while all but seven offer keyword search. Thirty eight also offer checkbook detail on subsidies intended for economic development. Other factors considered in grading included clarity about what was left out, the ability for bulk data downloads and whether information was available on quasi-public agency spending.

The availability of spending information has grown over the past few years. As the chart below shows, just eight state sites offered tax expenditure reports in 2010, compared to 44 today. Keyword search more than doubled, and the number showing the projected benefit of economic development subsidies grew from just two to more than half.

Spending transparency is also relatively cheap, the report’s authors find. In many states, the sites were paid for from the existing budget. The highest-listed start-up cost was $2.2 million in Mississippi, but most states spent $200,000 or less — in some cases, much less. Annual operating expenses ranged from drawing from existing budgets to $431,000. And state wealth didn’t seem to have much of a relationship with transparency, the authors found.

“While states with smaller budgets may have more difficulty investing in topflight information technology systems, they may have an easier time wrangling agencies into conforming to data standards,” U.S. PIRG Education Fund’s Phineas Baxandall and the Frontier Group’s Benjamin Davis write. “Some states with small revenue streams earned high transparency scores, while some states with large revenue streams earned low scores.”

No state was perfect, though. More information could be made available on quasi-public agency spending, they write. And nearly half the states don’t make clear what information is left out of online databases. Search and downloadability could stand to be improved in some states, too.