As the calendar turns to July, MBTA riders will be paying more to get around. To cap off a disastrous month for public transportation in Greater Boston, fares will go up for buses, subways, trains, and boats.

Thousands of us will be chipping in, fifteen cents at a time, to improve the system so we can have a more reliable ride in the future.

Or is the increase just natural inflation to pay for the rising cost of an aging system?

Or just chipping away at the MBTA’s debt and deficit?

It is unclear what exactly the fare increase will pay for. The answer may be all three of these possibilities, or others. Money is fungible, and any dollar spent on one project is a dollar not spent on another. Those fifteen cents spent on the new orange line cars or old Big Dig debts or T pension fund shortfalls are fifteen cents that aren’t being spent on healthcare or schools.

This notion that money can be used for different things and we must rank our options is commonplace in the daily lives of individuals and families. Eat out for dinner or pay down a little more credit card debt? Take an Uber home from a late night of work or wait for the Red Line? OK, bad example.

While this line of thinking is straightforward when we are in control, it is anathema to most politicians.

Considering the opportunity cost of policy choices forces prioritization, which is a word even dirtier than privatization in some "progressive" circles. Refuting the existence of opportunity costs and choices takes many forms, usually implicit but sometimes made explicit: “We shouldn’t have to choose between x and y” is a favorite boilerplate talking point for many politicians on the left.

One such choice between an x and y has been allowing the MBTA pension fund to operate in a vacuum, without basic levels of good governance and transparency. Taxpayers and T riders have responsibility for the fund’s losses, but have lacked any control over how the pension money is invested.

To put the magnitude of this choice in perspective, the total revenue raised by the fare increase next fiscal year is estimated at roughly $30 million. Every single day, hundreds of thousands of Massachusetts residents will be chipping in an extra fifteen cents out of their pocket. At the end of the year, all those nickels and dimes will add up to about what the MBTA pension fund lost in a ponzi scheme.

The absence of prioritization and acknowledgment of opportunity cost is, well, usually good politics - in the short-term. Democrats taking a PAC check from the Carmen’s Union and avoiding pension fund oversight make it easier to win re-election tomorrow. But if dozens of elected officials do that for decades, there will be consequences (say, a long string of Republican governors).

Speaking of Republicans, they have it much easier, with a simple message: less government, lower taxes. Making the implications of their choices clear is almost always a loser, so they stick with that general attitude: less, fewer, lower, and so on.

Democrats believe in a positive role for government, which increases the necessity to make policy choices clear. Democrats believe in raising taxes to spend it on things like better healthcare and schools. When you are raising, adding, and improving, you get to talk a lot about better lives. Democrats generally want to improve lots of different lives: victims of opioid abuse or a broken criminal justice system, hard-working school teachers and nurses, students from pre-K to college who represent our future.

It’s far harder to talk about how choosing one program to benefit one program means money that can’t go to another program.

Bernie Sanders wants to cancel all college debt for students from all income backgrounds. But that isn’t just a yes-or-no choice. There are opportunity costs to that policy decision. I recently had $125,000 in student loans from business school, which included funding a trip to Europe to advise a billionaire alumnus (for credit!). Bernie giving me $125,000 for graduate school debt means not giving a tax credit to 100 parents to pay off $1,250 in credit card debt from buying diapers and groceries. Or implementing evidence-based accountability measures and targeting a broader range of expenses (including housing) for lower-income students seeking a bachelors degree.

As voters, our job is to resist politicians’ pleas to forget about opportunity cost—and to demand that they be clear about their priorities. For Democrats, this path may feel like harder politics. But will bear fruit -- in a more effective government and more political power.

Liam Kerr is the Massachusetts director of Democrats for Education Reform.