TRENTON -- New Jersey's credit rating on Monday was dropped for a record 10th time during Gov. Chris Christie's administration.

The new rating, though still investment grade, signals the state's fiscal struggles, including slow-to-grow revenues, a growing retirement debt burden and intensifying budget pressures.

Here is what you need to know:

What happened yesterday?

Standard and Poor's Global Ratings cut the state's credit rating from "A" to "A-". The agency in March lowered the state's credit outlook from "stable" to negative," but at the time affirmed the "A" rating on New Jersey's general obligation bonds.

In addition to cutting the credit rating, S&P maintained the Garden State's negative outlook.

"We have kept our outlook at negative, reflecting lack of significant progress, in our opinion, in New Jersey addressing its very large pension funding gap," S&P analysts said.

What does that mean?

A credit rating is much like your own credit score. It reflects the likelihood the state will be able to pay its debts. A lower credit rating can result in higher interest rates, making it more expensive for the state to borrow money.

If the state has been hit with 10 downgrades, how is it still "A-"?

Those are the combined actions of the three ratings houses: S&P, Fitch Ratings and Moody's Investors Service. Fitch and Moody's have each downgraded the state three times under Gov. Chris Christie's administration. S&P has now done so four times.

How does the rating compare to other states?

New Jersey remains the second-lowest rated state, ahead of Illinois. S&P in October cut Illinois one notch to BBB -- two steps above junk territory.

Why was New Jersey downgraded?

The primary reason cited was the state's high unfunded pension liabilities -- the common culprit.

As of July 1, 2015, New Jersey's state and local pension funds have just 37.5 percent of the funding it needs to pay for future benefits. That is based on new reporting standards that require the state to project lower investment returns and had bleak consequences for the state's estimates. The funding ratio is the lowest in the U.S.

New Jersey's state and local pension funds had slightly more than $217 billion in liabilities and $81.4 billion in assets, leaving it with $135.7 billion in unfunded liabilities, up from $113.1 billion as of July 1, 2014.

"Pension liabilities are very high compared with other states," analysts said. "We calculate the state's share of net pension liability in 2015 as a very high 17.8% of state personal income and $10,648 per capita."

Analysts also blamed slow first-quarter tax collections, disappointing pension investment returns and the high-profile deal struck among lawmakers to cut more than $1 billion a year in taxes in exchange for a gas tax hike to fund the Transportation Trust Fund.

The estate, income and sales tax cuts in the trust fund package will cost the state budget about $1.1 billion a year by 2021, making it harder to pay for things like education and employee health care. At the same time, the state will bring in more than $1 billion a year for the trust fund that can only be spent on road, bridge and rail projects.

"While this loss alone might be manageable in the context of an overall $34.5 billion fiscal 2017 budget, it adds to the structural budget deficit and reduces our confidence in the state's ability to tackle long-term pension reform," the agency said.

It also cited the state's relatively low reserves, which the state tapped last year to patch a budget shortfall, and slow growth in revenues, particularly personal income tax collections.

How can the state improve its credit rating?

One way is by lowering its unfunded liabilities. This can happen two ways: either the state reduces its liabilities, what it owes to current and future retirees, or by increasing its assets through higher contributions and better investment gains.

Christie has been gradually increasing annual payments into the pension system, though not at levels agreed to under a 2011 pension overhaul. That landmark reform deal was invalidated by the state Supreme Court.

In its place, public worker unions are seeking a constitutional amendment that would require the state keep to a payment schedule.

Christie has also proposed sweeping reforms to benefits that would move employees onto less generous health care plans and into a "hybrid" defined benefit-defined contribution retirement system.

State Treasury spokesman Willem Rijksen said the latest downgrade "effectively amounts to another call for further pension and health benefit reforms, which the governor repeatedly has said are necessary."

Samantha Marcus may be reached at smarcus@njadvancemedia.com. Follow her on Twitter @samanthamarcus. Find NJ.com Politics on Facebook.