I don't know precisely what the default rate is, but I represented a bail bondsman for several years so I do have a good sense of the economics of that business.
Basically, bail bond business make very little profit after their expenses (rent, payroll, licensing, cost of use of money put up as bonds, etc.) on the non-refundable fees that they charge for the bonds themselves (typically about 10% of the bond amount although prices vary on a case by case basis). Additional fees are charged for security measures taken by the bail bond company to insure the client's attendance such as ankle bracelets or fees paid to bounty hunters to recover the client if he absconds.
The profits come almost entirely from seizing collateral (often motor vehicles, firearms and homes) that someone paying for a bond pledges in the event that the bail bond is forfeited, for example, because the criminal defend absconds rather than appearing at a hearing or trial, in addition to the non-refundable fee charged to provide the bond in the first place. (It is a bit like movie theaters which break even on their movie ticket revenues and make their profits by selling food and drinks.)
A typical bail bond business owner will sell the motor vehicles and firearms pledged as collateral to pawn brokers and independent used car sales lots, and will keep the (typically very bottom of the market) real estate and rent it to low income tenants. In other words, most bail bond company owners eventually build wealth by becoming slum lords with real estate pledges as collateral for bonds that go bad.
Another revenue stream for a bail bond business is bounty hunter work, partially for their own absconded clients which can result in a partial or full restoration of the funds provided by the bail bond company that often does not result in a refund to the client whose collateral was seized as a result of the default, and sometimes for other wanted felons upon whom law enforcement has placed a bounty because they are not set up to recover the subject of some of their outstanding warrants in an economically viable way. Usually, bounty hunting one's own absconding clients is more profitable than chasing reward money from law enforcement agencies for other people subject to arrest warrants.
Default rates are ultimately a function of how selective a bail bond company is about the clients for whom it posts bonds and about how closely the company supervises the client who is out on bond to make sure that he (or she) complies with his (or her) pre-trial release order terms.
But, even if the client absconds and the bail posted by the bail bond company is forfeited and can't be recovered within any applicable grace period, the bail bond company can still avoid losses by having collateral securing the risk of a forfeiture of the bond that is worth significantly more that the amount of the bond posted by the bail bond company.
As a typical bail bond company website (which sounds more clear than it is when you really try to pin down what they are saying and for what it is worth is not my former client's website) explains:
Most of the time bail collateral takes the form of property. If the
court is collecting on a property-based bail collateral because of a
failure to appear in court, it typically involves the seizure and sale
of the individual’s home. Property bail takes weeks to collect on, and
equity in the estate being sold must be determined to equal at least
150% of what is owed the court.
Collateral will be returned when the case is completed, whether the
the person is found innocent, the charges are dropped, the person is
sentenced or bail is exonerated. If the individual for whom the bail
collateral was offered fails to appear in court at the agreed upon
time and date, the collateral will be seized or collected by the court
or the bail bond company.
The full amount of the collateral may not be returned to the
individual if a premium has been put in place when using a bail bond
agent. This premium is negotiated between the bail agent and the
arrested party or person bailing the arrested person out. Bail
collateral will typically be returned within five business days after
the individual has paid off all financial obligations and their case
has been concluded. Until this happens a bail bond agent can hold the
A financial website explains the situation this way:
When a defendant uses a bail bond agent to post bail, the defendant
must pay the bondsman’s fee, and may also have to hand over collateral
or sign a security agreement. Should the defendant comply with bond
conditions, the bond agent will return the collateral or release the
lien created by the security agreement upon the conclusion of the
case. However, the bond agent’s fee (the 10% to 15% of the total bail
amount) is not returned no matter the outcome.
Bond Forfeiture and Bounty Hunters
Should a defendant who used a bond agent’s services fail to appear in
court or otherwise violate bail terms, the agent can usually try to
find the defendant, take that person into custody, and physically take
the defendant back to police custody. Courts typically grant bond
agents a grace period after a defendant violates bail terms. If the
agent can return the defendant to court within that grace period, the
court usually will not require the agent to pay the full bail amount.
As part of this process the bail bond agent can employ bounty hunters,
also called bail enforcement agents, to track down and apprehend the
defendant. Bounty hunters, like bail bond agents, are not government
employees or law enforcement officers. They do not have general arrest
powers, but can arrest a defendant who used the bail bond agent’s
services. This is because as part of the contract defendants sign with
the bail bond agent, defendants typically agree to allow the bond
agent, or bounty hunters working for the agent, to enter their home,
arrest them, or take other actions that would typically be illegal
without the defendant’s consent.
Note that state laws on both bail agents and bounty hunters can differ
significantly, and not all states allow for bail bond agents or bounty
For example, suppose that son is arrested for a felony and released prior to trial on a $20,000 bond for which his parents pay a non-refundable $2,000 non-refundable premium and sign off on a $20,000 second mortgage on their house with a $200,000 fair market value which is also subject to a $160,000 first mortgage. If son defaults in a way that triggers his parents' obligation to pay the $20,000 placed at risk by that default, and the parents don't have the money, the bail bondsman takes the house subject only to the $160,000 first subprime mortgage and nets $40,000 of equity (the $20,000 surplus would rarely be enough to cause another buyer to bid at the foreclosure sale).
The bail bondsman then refinances the $160,000 first mortgage at the much lower interest rate he qualifies for with his higher net worth and better credit rating, and then rents it (often initially back to the parents who pledge the house as collateral in the first place) at a market rate, which, for a house like that is probably on the order of $2,000 a month, until he decides to resell it (perhaps assembling many similar houses on the same block over time and then selling the entire block to a developer who wants to scrape the houses to build an apartment building on the entire block instead, at a significant premium).
Even if I a mistaken and the collateral can only be seized when the bond is actually forfeited and not merely when it is placed in peril by a failure to appear when the grace period has not yet run, or if the actual amount of the bail bond debt is repaid after the collateral has been foreclosed upon and sold to a third party, insuring that there is sufficient collateral to back the full amount of the bond if it has to be repaid to the bail bondsman, this still prevents the bail bondsman from losing any money in the worst case scenario if the bond is forfeited. Indeed, this will usually make the bail bondsman a healthy profit because the value of the collateral is generally significantly in excess of the value of the bond, at the cited bail bond company at least 150% of the amount potentially owed (also providing a cushion if the fair market value of the collateral has been overestimated), but not so high relative to the value of the bond that another bidder will bid at a foreclosure sale. So the bail bondsman will sometimes make a profit on the collateral seizure and sale to a third-party, even if the bond debt ($20,000 in this example) is ultimately repaid to the sponsors of the client because the client is returns to court custody before the grace period expires.
Sometimes a bail bondsman will also take a guarantee of repayment of the bond amount if there is a default, in place of some or all of the collateral if the guarantors' incomes are sufficient to comfortably be able to pay the full bond amount, at least in installments over time, even if the guarantor has few assets of value to pledge, but this is much more common for small bonds of, for example, $500 or $1,000 or $2,000 than it is for a medium bond amount for a felony of about $10,000 or a higher amount of $25,000 or $100,000 for serious felonies when the court is worried that the client is a flight risk, where the bail bondsman will typically post bond only of the client's supporters can offer sufficient collateral to cover the full amount.
This is very similar to the reason that a hard money lender doesn't worry too much about the ability of the people borrowing from the hard money lender to pay during the typically short loan term because any unpaid loan balance can be recovered by seizing collateral for the hard money loan which is worth significantly more than the value of the loan.
The New Yorker interviewed a bail bondsman who claimed that less than 1% of his clients defaulted, in 2013, but in my experience this is highly implausible and unusual (as the story notes, even prime secured mortgage loans have a higher default rate than that most of the time), even though it certainly isn't impossible if one is very selective about who one takes on as a client. The more likely possibility is that the bail bondsman is actually talking about clients who abscond or violate bond conditions who are not returned to the court within the grace period, or about the percentage of transactions in which the bail bondsman actually loses money after foreclosing on collateral and collecting from guarantors, if necessary.
A New York Times in a 2018 article does not provide a forfeiture rate figure, but does explain that as long as the client is returned to law enforcement authorities within a grace period that can vary from a few months to two years on a state by state basis, the forfeited bond will usually be returned to the bail bond company.
One company cited in the 2018 New York Times article with $800 million of revenues had zero losses as a result, a data point that I strongly suspect reflects not a zero bond forfeiture rate but a complete recovery of forfeited bonds from bond collateral and guarantors, with profits on some bond collateral seizures exceeding, on average, losses from bonds extended with insufficient collateral or with guarantors who can't make good on their obligations or go bankrupt.
According to this 2018 New York Times article, California is one of the only states that requires a premium refund when a client is re-incarcerated voluntarily during the grace period.
This policy white paper from the Obama Administration notes that:
Though failure-to-appear rates declined from 25 to 17 percent between
1992 and 2009, pretrial re-arrest rates actually increased from 14 to
16 percent for released felony defendants in large counties.
This 15-17% failure to appear rate is a much more accurate estimate of bond defaults prior to before considering grace periods.
A law review article from 1994 explores the economics that drive the bail bond industry in more detail than is possible in a Law.SE answer.