In reality, Underwriting is advertising that simply conforms to the specifics set forth by the FCC that regulates the content.
If you check some of the financial statements from lots of Public Radio stations, listener funding is not the majority of income at most stations. Likewise, underwriting is typically not far removed from the listener memberships. From the stations I've checked, grants seem to be very important and many stations invest in non-radio revenue sources. They might own a music or arts venue, an office building or have a spun-off company selling product of interest to the radio listener. It seems many stations have 'diversified' their dollars to have them working on several levels and many times, perhaps related to radio, are not always dependent on the station to produce income. That way if one segment of revenue falters, it is easier to recover from.
I guess it is sort of like a guy I knew that started a Church. Once they needed a building, they bought a small strip center in the neighborhood, put the Church at one end and leased the other units. The result was the Church could cover the mortgage payment and the rent paid for the Church's operating expenses.
Granted, this is not across the board, but traditionally the listener membership side is typically not as much of a factor as the underwriting and many times the grants and 'other income' exceed the amount gained from underwriting and listener contributions. On the other end, there are some heritage-like stations that are fully reliant on listener memberships for survival.
Underwriting at some stations is viewed as a needed evil, so at those stations, underwriting is a lower percentage. On the other hand, there are some stations that consider listener memberships as icing on the cake and push underwriting and grants since you need such a large number of regular listeners to get enough money to matter.
I really doubt the standard commercial will every show up on your neighborhood NCE station.
