Since Proposition 47 was adopted in 2014 the homeless population in California has soared nearly 60 percent, even though it is falling in two thirds of other states.

We all see the terrible human cost paid by those suffering on our streets. But beyond those human costs are the hard costs paid by state and local governments to care for, manage, and work to bring people indoors. Statewide, local governments spend over $50,000 per homeless person per year managing the immediate impacts of unsanctioned encampments. That means the total cost associated with simply managing street homelessness paid for by our tax dollars is now up to $9 billion dollars a year.

Proposition 47 isn’t the only factor in a homelessness crisis caused by a lack of basic shelters, lack of mental healthcare beds, a growing drug epidemic, and the overall high cost of housing. But a growing number of experts agree that when we took away the ability of judges to require people with multiple convictions to go into treatment we took away a proven tool to help people get their lives back together and stay off the streets. And we are all now paying for that decision every day – with the costs in dollars now measured in billions.

Beyond the human and financial costs of our rising homeless population, we are also paying the price for the rising number of retail thefts that have now reached crisis levels in many communities. Statewide last year, the cost of retail thefts in California was $7.8 billion – and that’s a financial burden we all pay at the checkout counter. Again, we can trace a significant part of these higher costs to the passage of Proposition 47, which made thefts under $950 misdemeanors with minimal consequences, even if a suspect steals $950 every day of the year.

Proposition 47 was well intentioned, and I myself voted for it. We were right to want to end the era of mass incarceration. Prop. 36 doesn’t undo this important outcome. But it does close      gaps in that law which have created a host of unintended consequences in our communities.

The fact is that we are now paying a terrible human cost – and financial penalty – because we took away the ability of judges to order people into treatment and the incentive for more people in the criminal justice system to accept treatment.

Since Prop. 47 passed ten years ago, drug overdose deaths have more than doubled — becoming the leading cause of death for Californians aged 15-44. Alongside Prop. 47, much of this can be traced to the introduction of deadly fentanyl into our state. When we took away mandatory treatment, we took away a tool that we now need more than ever as fentanyl is significantly more addictive and deadly than hard drugs from earlier eras.

Fortunately, there is an answer that will save money and lives. Proposition 36 will bring back court mandated treatment, create accountability for those engaged in multiple acts of retail theft, including a treatment option when relevant, and create tougher sanctions on those selling fentanyl.

It is common sense, and it certainly makes financial sense. Studies show that for every dollar spent on treatment we can save between up to $7 in reduced criminal justice costs.

Proposition 36 is at its core a measure to bring back the requirement and incentives for treatment for those committing nonviolent crime driven by addiction. Successful substance abuse treatment will reduce our homeless population, help prevent many retail thefts, and      save the lives of Californians dying in record numbers from preventable drug overdose deaths.

When you hear from some opponents of Proposition 36 that it will “cost too much,” they are simply not accurately accounting for the terrible human and financial costs of the flaws in Proposition 47 – flaws that we can fix by passing Proposition 36 this November to save money and lives.

Matt Mahan is the Mayor of San Jose and co-leader of a statewide campaign committee set up to Reform Proposition 47 by passing Proposition 36.