PHOENIX - We've received several requests from teachers and parents to verify the "What If" TV ad that has aired in the Phoenix market since January.

The ad's cheery narrator begins: "What if I told you there's a state that has increased education funding by nearly $1.5 billion in the last three years?"

The upbeat ad was created to counter parent and teacher groups sounding the alarms over Arizona's bottom-five-in-the-nation rankings for teacher pay and per-pupil spending.

A new group called the Arizona Education Project paid for the ad. Republican Gov. Doug Ducey's major business supporters - the parent company of Arizona Public Service, the state's largest business and tourism groups - finance the Arizona Education Project.

The ad's timing coincides with the governor's re-election campaign this year. Education will be a major theme.

It makes a big claim: There has been $1.5 billion in new spending on schools in the last three years.

That all depends on how you count to $1.5 billion, what's in that $1.5 billion and whether $1.5 billion is even right.

Let's do the math, based on data compiled by the independent Joint Legislative Budget Committee.

According to a spokesman for the Arizona Education Project,

the numbers are based on what the state spent on K-12 schools in 2015, the year Ducey took office.

The ad arrives at $1.5 billion through "cumulative government accounting."

Follow along with me:

- Starting in 2016 - Ducey's first budget - K-12 funding was $409 million more than in 2015.

- In 2017, K-12 spending was $516 million above 2015 levels.

- And in 2018, it's $822 million more than in 2015.

The grand total in this accounting method: $1.7 billion more dollars for K-12 (not $1.5 billion) than in 2015.

The rationale is that every additional dollar spent in each year after 2015 is considered "new."

It's fair to say that most of us don't count this way.

Say I got a raise from $25,000 a year to $50,000 next year and then $75,000 the year after that and $100,000 the year after that.

I would be thrilled with a $75,000 raise over three years.

Using cumulative accounting, my boss could burnish his generosity by saying he has increased my paycheck by $150,000 over three years.

Leaving aside accounting methods, the ad doesn't disclose where most of that $1.5 billion came from.

Arizona voters' approval of Prop 123 in May 2016 has delivered $900 million to K-12 schools, according to JLBC data.

The Prop 123 cash, a projected stream of $3.5 billion over 10 years, was the governor and Legislature's negotiated way of paying back most of the billions of dollars that judges said the state owed to its schools.