What Defines the Modern Embedded SIM
eSIM vs Physical SIM Card Which One Is Right for You
Swapping SIM cards when you travel or switch carriers can be a hassle, which is where the eSIM vs physical SIM comparison comes in. A physical SIM is a removable plastic card that stores your mobile network credentials, while an eSIM is a tiny, embedded chip built directly into your phone that you activate with a quick scan of a QR code. The eSIM lets you switch networks or add a second line without ever needing to find a tiny tray pin, making it a flexible, convenient alternative.
What Defines the Modern Embedded SIM
The modern embedded SIM is defined by its permanent, non-removable hardware, contrasting sharply with the removable physical SIM’s form factor. Unlike a physical card that is inserted and swapped, the eSIM is soldered onto the device’s motherboard, requiring a digital profile download to activate a carrier. This integration frees up internal space for larger batteries or slimmer designs. Its core advantage is remote provisioning, allowing users to switch between carriers or add a second line entirely via software, without sourcing a new physical card. This makes dual-SIM functionality far more seamless, as you can hold multiple profiles simultaneously. However, this convenience places absolute trust in the device’s software for all carrier changes, eliminating the physical fail-safe of simply moving a card.
Inside the architecture of a reprogrammable chip
Inside the architecture of a reprogrammable chip, such as an eUICC, the core difference from a physical SIM lies in its rewritable memory. Unlike a soldered, read-only ROM on a physical card, this chip contains a secure, partitioned flash memory. An embedded operating system manages isolated sandboxes called ISD-Ps, each capable of holding a unique carrier profile. To switch networks, a sequence of secure remote provisioning commands writes a new profile into an empty ISD-P, entirely overwriting the previous active profile without requiring a swap of plastic. This architecture allows one chip to logically store and activate multiple profiles over its lifetime.
- A provisioning agent establishes a secure connection with a remote SM-DP+ server.
- The server encrypts and downloads the new carrier profile into an unused partition.
- The chip’s OS validates the digital signature, then activates the new profile, disabling the old one.
How remote provisioning changes connectivity
Remote provisioning changes connectivity by letting you switch carriers directly from your device’s settings, skipping the wait for a new plastic SIM to arrive. This means you can activate a local data plan instantly when you travel, without hunting for a store or swapping cards. It also lets you manage multiple profiles on one chip, so you can keep your home number active while testing a secondary provider. Instant carrier switching thus removes physical delays entirely, making connectivity feel as fluid as toggling a Wi-Fi network.
Key profiles and carriers supported without swapping
A defining advantage of the modern embedded SIM is that it supports multiple carrier profiles simultaneously without requiring a physical swap. Users can store and switch between several active profiles, such as a primary home network and a secondary data-only travel eSIM, directly from device settings. This eliminates the need to carry or exchange physical SIM cards when changing providers or adding a temporary line. Each profile is isolated and remains dormant until selected, ensuring no accidental billing overlap.
- Ability to store 5–10 carrier profiles on a single eSIM chip
- Instant activation of a new profile by scanning a QR code from a carrier
- Simultaneous support for a local and an international carrier without powering down the device
Legacy SIM Cards Still in Your Pocket
Many people carry legacy SIM cards in old phones or forgotten devices, often tied to grandfathered plans with unique perks. Switching to an eSIM can render these physical cards obsolete, but porting your number from a legacy SIM to an eSIM is a straightforward process that preserves your existing service. However, the legacy SIM profile must be deactivated after transfer, or the card becomes useless. Unlike a physical SIM, which can be physically removed and reinserted, an eSIM lacks a tangible form, so the legacy card simply becomes electronic waste. For dual-SIM users, keeping a legacy SIM in a secondary slot can still work for temporary roaming on a secondary carrier, though an eSIM offers a cleaner solution without the need for a physical insert.
The familiar plastic form factor and its variants
The familiar plastic SIM, a tiny, removable card, comes in several form factors you might still carry. The standard, mini, and micro versions persist in older devices, while the smaller nano-SIM remains the current physical standard for most modern phones. Its size is deceptively crucial, as accidental misplacement often leads to a frantic drawer search. When comparing to eSIM, the plastic card’s tangibility is its key trait—you can physically swap carriers by swapping cards. Q: Can I cut a larger SIM down to a nano-SIM size? A: Yes, but only if the original chip placement aligns; otherwise, you risk damaging the contacts.
Why physical cards remain a global standard
Physical SIM cards maintain global dominance through their immediate, universal compatibility. Unlike eSIMs, which require device and carrier support, a physical card works in virtually any unlocked phone, making it the failsafe for travelers and users swapping devices. This form factor provides tangible network access without software setup or QR scans, critical when battery or connectivity is low. The card’s physical removal also offers a clear, irreversible way to switch networks, eliminating the risk of lingering carrier locks or digital provisioning errors that complicate eSIM management.
Storage limits and security features embedded in the card
A physical SIM card has a tiny built-in memory that can store a limited number of contacts and text messages, typically around 250. These security features embedded in the card protect that stored data, but the card itself is easily stolen. Unlike an eSIM soldered into your phone, a physical SIM can be physically removed and inserted into a new device, bypassing your phone’s lock screen. The eSIM, however, keeps that storage and security tied directly to your device’s operating system, making it impossible for someone to simply pop out your identity and wallet of stored contacts.
Activation and Switching: Speed vs Simplicity
Activation and switching priorities differ distinctly between eSIM and physical SIM. A physical SIM card offers absolute simplicity: you insert it, it works instantly, with no technical setup. Its speed is limited by obtaining the physical card. eSIM activation is potentially faster for digital purchases, often completing in minutes, but requires scanning a QR code or entering details, adding a step. Switching between carriers on eSIM is rapid—you download a new profile without waiting for mail—but simplicity suffers if you manage multiple profiles in software. Q&A: Is eSIM always faster for switching? Not for simplicity; a physical SIM swap is simpler but slower if you lack the card. The physical SIM’s mechanical swap is slower but foolproof, while eSIM favors speed at the cost of a learning curve.
Scanning a QR code versus inserting a tray
Activating an eSIM by scanning a QR code versus inserting a tray eliminates the physical delay and fragility of swapping nano-SIMs. With a QR code, you complete activation in under a minute by simply pointing your camera at a provided image or email attachment. This avoids fumbling with a SIM ejector tool, locating the tiny tray slot, and handling a card that can easily be lost or damaged. Inserting a tray requires powering down the device, applying precise pressure, and aligning the chip perfectly. For on-the-go switching, scanning a QR code is faster and more reliable, removing the risk of dropping or breaking the physical card. The process follows a clear sequence:
- Open settings and select mobile network.
- Choose “Add eSIM” and point the camera at the QR code.
- Confirm the plan activation within seconds.
Managing multiple carriers on one device
Managing multiple carriers on one device is far simpler with eSIM, as you can download several profiles without juggling tiny plastic cards. Physical SIMs limit you to swapping trays—a hassle when traveling. With eSIM, switching carriers often takes just a tap in settings, offering seamless multi-carrier management for work and personal lines. You can even keep a physical SIM alongside eSIMs for even more flexibility.
- Store several carrier profiles simultaneously on one device.
- Switch active data plans instantly without removing anything.
- Mix a physical SIM with multiple eSIM profiles for extra options.
Time saved during travel with instant profile download
Travel time is directly reduced because instant profile download eliminates the need to visit a local store or wait for a physical SIM delivery. Upon arrival, users simply scan a QR code or install an app, activating connectivity within seconds. This removes the friction of hunting for a vendor or dealing with registration paperwork. The saved minutes compound across multiple destinations, bypassing queues that physically swapping SIMs would otherwise require.
- No queuing at airport kiosks or local carrier shops.
- Activation occurs before landing, enabling immediate use upon exiting the terminal.
- Data profiles download over Wi-Fi, so no time is lost searching for a physical slot or tool.
Device Compatibility Across the Market
Device compatibility across the market creates a stark divide. eSIM support remains largely exclusive to recent flagship smartphones, leaving budget and mid-range devices reliant on the physical SIM card. Even among compatible handsets, users often face carrier lock—a phone may technically support eSIM but be blocked by the provider.
Meanwhile, the physical SIM’s universal slot works in every unlocked phone from the past decade, from basic feature phones to aging iPhones.
If you buy an unlocked eSIM-only device abroad or switch carriers frequently, the physical SIM offers seamless cross-device portability, while eSIM can strand you if your next phone lacks support.
Flagship phones that have already removed the slot
For users considering the switch, flagship phones without a physical SIM slot have already made the choice for you. Devices like the US iPhone 14 and later, alongside certain Pixel 8a models, force reliance on eSIM activation from the first power-up. This eliminates the ability to swap carriers instantly or use a local prepaid chip while traveling. Before buying, verify if your carrier supports eSIM transfer, as these phones lack the backup of a removable card, locking you into digital profiles for every plan.
Budget and mid-range options clinging to the tray
For budget and mid-range smartphone users clinging to the tray, the hybrid SIM slot is the primary compromise, forcing a choice between a second line and expandable storage. These devices rarely support dual standby eSIM, so the physical tray remains essential for cost-conscious users reliant on prepaid data plans. This physical dependency means even a phone with eSIM capability still requires tray access for primary carrier activation.
- Hybrid trays block concurrent use of nano-SIM and microSD in most sub-$300 models.
- Dual-SIM standby on mid-range trays drains battery slower than eSIM-based dual activation.
- Tray-reliant users cannot use eSIM-only international roaming without first swapping out their physical card.
Tablets, smartwatches, and IoT gear leading the shift
For tablets, smartwatches, and IoT gear, eSIMs are making the big switch a no-brainer. You don’t have to pry open a waterproof smartwatch or fiddle with a tiny tray in a tablet just to swap networks. This hardware-free connectivity for compact devices means a fitness tracker can grab its own data plan without needing a physical slot, and a smart sensor can be deployed anywhere without a carrier visit. It’s simply a cleaner, more durable setup for gear that’s often too small or too sealed for plastic SIMs.
Tablets, smartwatches, and IoT gear lead the shift by eliminating SIM trays, making multi-device connectivity seamless and rugged.
Security and Theft Protection Compared
A physical SIM card can be physically stolen from your phone, giving a thief direct access to your number and the ability to bypass two-factor authentication (2FA) codes sent via SMS. In contrast, an eSIM is embedded in the device’s motherboard and cannot be removed if the phone is stolen. This makes eSIM inherently more resistant to SIM-swap attacks via physical theft, as there is no card to extract. However, if a thief gains remote access to your carrier account, they can still provision a new eSIM onto their own device, so
The security advantage of eSIM depends entirely on how tightly your carrier locks account changes behind strong authentication, such as biometrics or a physical security key.
Locking your carrier account is as critical as locking your phone.
Why a digital profile is harder to clone or remove
A digital eSIM profile is inherently harder to clone than a physical SIM because the Integrated Circuit Card ID (ICCID) and authentication keys are not stored on a removable chip. Instead, they are securely embedded in the device’s tamper-resistant hardware, making them inaccessible to physical extraction or skimming devices. Removal also requires a deliberate action: you must access the device’s settings and intentionally delete the profile, which often demands biometric verification or a PIN. A thief cannot simply eject the SIM to sever the connection or steal the identity, as the profile is locked to the specific eUICC chip inside the phone.
Q: Why is an eSIM profile harder to clone than a physical SIM?
A: Because the digital identity is stored on the device’s soldered secure element rather than a removable chip, preventing physical access for cloning tools or side-channel attacks. Removal also requires authenticated software steps, not just hardware manipulation.
Physical card theft and emergency disabling methods
A physical SIM card is inherently vulnerable to theft; removing it from a device grants instant access to the carrier account and two-factor authentication codes. Emergency SIM card disabling relies on contacting the carrier to suspend the line, which can be delayed by account verification requirements or poor reception. eSIMs mitigate this by being embedded and requiring device authentication to transfer, meaning a thief cannot simply remove the card. Disabling an eSIM line can often be done instantly via the carrier’s app or web portal, even if the device is offline, because the eSIM profile is remotely deactivated on the network side.
Q: How quickly can a physical SIM be disabled after theft compared to an eSIM?
A: A physical SIM requires carrier call or chat support, often taking minutes to hours due to verification steps. An eSIM can typically be disabled in under 30 seconds through a carrier app or website, as the remote profile deletion takes effect on the network immediately.
Remote wipe capabilities built into eSIM-enabled devices
Remote wipe capabilities in eSIM-enabled devices target the profile itself, not just the device storage. Unlike a physical SIM, which must be physically removed to sever network access, an eSIM profile can be deactivated remotely over the air. If a device is lost, a user or carrier can push a command that instantly invalidates the embedded SIM profile, preventing the thief from using the cellular network. This stops unauthorized data routing through the eSIM and makes the device untethered from the mobile account. For comparison, a physical SIM would require manual deactivation of the account, leaving the card functional in the thief’s hands until that step is completed.
Remote wipe of an eSIM disables the embedded profile over the air, stopping cellular access immediately—unlike a physical SIM that remains usable until the account is manually canceled.
Roaming Convenience and Global Data Plans
For roaming convenience, an eSIM eliminates the need to swap physical cards when traveling, allowing you to instantly download and activate a global data plan before departure. This avoids losing your primary number and searching for local SIM vendors abroad. A physical SIM, however, restricts you to carrier-provided roaming packages, which are often more expensive and require a physical purchase. Quick Q&A: Which offers better global data flexibility when crossing multiple borders? The eSIM wins, as you can stack or switch between regional plans in-app, whereas a physical SIM locks you to one provider until you replace it.
Local carrier access without swapping cards abroad
With a physical SIM, accessing a local carrier abroad requires physically sourcing and swapping the card, which risks losing the original or damaging the slot. An eSIM eliminates this friction entirely, allowing users to purchase and activate a local data plan digitally before or during travel. A traveler can thus bypass airport kiosks and maintain their primary number for calls while using a local network for data, all without handling a tiny chip. This provides instant local network activation without card swapping, as the profile downloads directly to the device and can be toggled on or off alongside the home line.
Prepaid data bundles from international eSIM providers
For global travel, prepaid data bundles from international eSIM providers are a game-changer. You skip the hassle of swapping your physical SIM at an airport kiosk or paying your home carrier’s sky-high daily roaming fees. Instead, you buy a bundle online—like 5GB for a week in Japan or unlimited data for a South America trip—and activate it instantly via QR code. Your calls and texts on your primary number stay active, while you jump on a local data network abroad. It’s like having a spare, local phone in your pocket without ever touching a piece of plastic.
- Choose bundles by region or country, tailored to your trip length.
- Top up via app or website instantly if you run out of data.
- Keep your existing SIM in the phone for dual numbers—no physical swap needed.
Eliminating the risk of losing the original card while traveling
Traveling with a physical SIM card carries the constant risk of losing or damaging the tiny chip, especially when swapping it out for a local plan. An eSIM eliminates this hazard entirely because the original number stays embedded in the device’s hardware, never requiring removal. This ensures your home line remains accessible for two-factor authentication and emergency contacts. Eliminating card loss during transit also removes the need to carry a SIM ejector tool or a secure storage case for your primary card. Q: Does an eSIM protect against losing my home number while abroad? A: Yes, since the eSIM profile is software-based and cannot be physically lost, your primary line remains safe in your device regardless of how many temporary plans you add.
When Dual SIM Actually Means Something Different
In the context of eSIM vs physical SIM, “Dual SIM” often misleads because it implies two active, always-connected lines. The real difference emerges when a device supports one eSIM and one physical SIM, but only the physical slot offers full, non-revocable control. With an eSIM, your second line can be remotely erased or reassigned by the carrier, making it a borrowed privilege rather than a permanent fixture.
A true, independent backup line requires a physical SIM in the second slot, as eSIMs can be deactivated or moved without your direct consent.
This means your emergency number, separate work profile, or roaming line is only genuinely yours if it’s kill-switch-proof—something only a removable chip guarantees.
Using two active lines without a second tray
Using two active lines without a second physical SIM tray relies entirely on an eSIM profile for the secondary line. You install the second carrier’s eSIM digitally, then configure your phone to use one line for data and the other for calls/SMS. Both lines remain simultaneously reachable, and you can switch data between them in settings. This eliminates needing to swap trays or carry spare SIMs. The main limitation is that many devices support only one active eSIM—if you also need a physical SIM for line one, line two via eSIM works as the sole digital alternative.
Combining a physical and digital SIM in one phone
Combining a physical SIM and a digital eSIM in one phone is a dual SIM setup for travelers that keeps your home number active while adding a local data plan. You pop in the physical card for your main line, then scan a Singapore eSIM QR code or download an eSIM profile for the second. This mix lets you avoid carrying two devices or swapping cards abroad. Your phone handles calls on one and internet on the other seamlessly. It’s a practical way to split work and personal lines too, without juggling extra hardware.
| Physical SIM | eSIM |
|---|---|
| Your usual home number | Local data on a trip |
| No QR scan needed | Instant activation via digital profile |
| Swapable between phones | Fixed to one device |
Work-life number separation made easier
Work-life number separation becomes effortless with dual SIM setups when you ditch physical swaps. An eSIM allows you to add a work number to your phone instantly without unseating your personal SIM. This means you can toggle a single work profile on and off, silencing after-hours calls while keeping your personal line always active. For clear separation, follow this sequence: first, activate your personal number on the physical SIM; second, download the work eSIM profile.Dual identity management then happens in your phone’s settings. Finally, mute work notifications during off-hours without touching your personal line at all.
Carrier Standoff and Adoption Hurdles
Carrier Standoff remains the primary adoption hurdle for eSIM. Unlike a physical SIM card, which you can swap instantly between any unlocked phone, eSIMs tie your profile to a specific carrier’s digital provisioning system. If your provider resists releasing the eSIM activation or refuses to transfer it to a new device without a store visit, you lose the seamless portability that makes physical SIMs universally compatible. This standoff forces users to choose between a locked eSIM profile or the instant freedom of a physical card. Until carriers standardize and automate eSIM transfers as reliably as SIM swapping, adoption will remain stalled by deliberate friction from providers protecting their customer lock-in. The practical result is that many travelers and multi-device users still carry a physical SIM as a failsafe against carrier gatekeeping.
Why some providers still resist full eSIM support
Some providers resist full eSIM support mainly to retain customer control. Switching carriers becomes frictionless with an eSIM, threatening lock-in tactics like requiring a physical SIM swap in-store. Providers also fear increased churn, as users can instantly activate a competitor’s plan without waiting for a card. Additionally, legacy retail and support systems are still optimized for physical SIM inventory and activation workflows. For many telcos, the predictable revenue from physical SIM logistics outweighs the operational efficiency eSIMs promise.
- Customer lock-in is harder to maintain without a physical SIM to withhold.
- Retail staff would require retraining away from familiar card-based sales.
- Existing billing systems often lack seamless eSIM provisioning integration.
- In-store accessory sales (SIM cards, adapters) would drop significantly.
Regulatory and licensing complexities in different nations
In the context of eSIM adoption, regulatory and licensing complexities across different nations create direct user friction. Some countries require local mobile network operators to issue eSIM profiles only after physical identity verification, mirroring traditional SIM registration laws. This means a traveler cannot simply download an eSIM remotely before arrival; compliance with local telecom licensing mandates physical presence. Conversely, other nations lack a legal framework for provisioning eSIMs at all, forcing carriers to rely solely on physical SIMs. A user moving between these jurisdictions faces fragmented availability, unable to seamlessly switch networks because the eSIM profile is legally blocked by local licensing rules.
Q: Why do some nations block remote eSIM activation while others allow it?
**A:** Local telecom licensing laws often tie an eSIM profile to the same mandatory identity verification (e.g., passport scan, in-person check) required for physical SIMs. If a nation’s regulatory framework does not recognize digital registration as valid, the eSIM cannot be legally activated without a physical encounter, regardless of carrier interest.
Consumer confusion around transferring profiles
Consumer confusion around transferring profiles stems from the lack of a universal, intuitive process. Unlike a physical SIM that is simply moved between devices, an eSIM requires locating a carrier’s specific portal, generating a new QR code, or downloading a profile, which varies by operator. Many users fail to realize that a profile is tied to a device’s unique identifier, not their account, leading to frustration when a phone is wiped or replaced. This ambiguity often results in accidental deactivation or loss of service, making profile portability a significant adoption hurdle for average consumers.
Environmental and Manufacturing Impact
The manufacturing of physical SIM cards involves extracting raw materials like plastic and metals, then molding, cutting, and shipping them, which generates waste and carbon emissions. eSIMs eliminate this entire physical production chain, as the profile is a digital file stored on an embedded chip already in the device. Does an eSIM reduce electronic waste? Yes, by removing the need for a plastic card and its packaging, eSIMs significantly lower material consumption and the disposal of obsolete SIMs. Furthermore, manufacturing a single physical SIM card produces roughly 0.001 kg of CO2, whereas an eSIM has zero manufacturing impact for the user beyond the device’s existing hardware. This practical shift means fewer natural resources are extracted and less industrial pollution is created per mobile connection.
Reducing plastic waste from millions of SIM cards
Switching to an eSIM is a super simple way to slash the plastic waste from those millions of tiny SIM cards. Each physical card comes in a larger plastic carrier that just gets tossed, creating heaps of non-recyclable junk. By skipping that entire manufacturing step, eSIMs eliminate this waste at the source. For the user, it means zero plastic trash to dispose of when activating a new plan, making it a genuinely cleaner choice right out of the gate. This directly targets the plastic waste reduction that comes from the sheer volume of cards produced globally.
Smaller device footprints and waterproofing benefits
Ditching the physical SIM card directly enables smaller device footprints and simpler waterproofing. Without the SIM tray and its internal slot, manufacturers can shave millimeters off a phone’s thickness or repurpose that space for a larger battery. Waterproofing gets easier too: you eliminate a major entry point for moisture. The process becomes a straightforward sequence:
- The chassis is designed with one fewer seam or gasket.
- The device can be sealed more completely, often reaching a higher IP rating without complex port flaps.
This means a truly water-resistant phone doesn’t rely on a rubber plug you might forget to close.
Supply chain simplification for telecom operators
For telecom operators, ditching physical SIM cards dramatically cuts logistical headaches. You no longer need to manufacture, package, or ship millions of plastic cards to stores. This reduces operational overhead by removing inventory management and warehousing costs entirely. Instead, you just push a digital profile over the air, which also eliminates the waste from unsold or expired stock.
Q: Does this really save operators time on setup?
A: Absolutely. Instead of waiting for a physical card to arrive in the mail, a customer can activate a line in minutes, meaning less back-and-end support for you.
Future Outlook Beyond the Slot
The future outlook beyond the slot for connectivity is defined entirely by eSIM’s ability to eliminate physical constraints. Once the physical SIM tray is gone, devices become permanently sealed, more water-resistant, and free of mechanical failure points. This unlocks remote provisioning as a default feature, allowing users to switch carriers or add data plans instantly without waiting for a plastic card. The physical SIM card is inherently static; it ties you to a physical object that must be inserted or swapped. Beyond the slot, eSIMs enable seamless management across multiple profiles on a single device, making dual-line or multi-network use practical without opening your phone. This transition renders the physical slot obsolete for all but legacy compatibility, pushing the entire user experience toward instant, slot-free activation and greater device durability.
iSIM technology merging the SIM into the processor
The most radical evolution in this space is iSIM technology merging the SIM into the processor, which eliminates the dedicated chip entirely. Unlike an eSIM, which is a soldered component on the motherboard, an iSIM buries the SIM function directly into the device’s main application processor or modem die. This integration shrinks physical space requirements to near zero and reduces power draw, boosting battery life for compact wearables. Users gain the same remote provisioning benefits as eSIM—switching carriers via software—without any physical part to damage or replace. For practical use, the device effectively becomes its own SIM infrastructure.
Predictions for a completely slotless smartphone era
In a completely slotless smartphone era, devices would achieve true monolithic waterproofing and enhanced internal space for larger batteries or advanced cooling. Users would manage all mobile connections exclusively through embedded software, allowing seamless profile switching without physical card handling. A primary shift involves instant carrier switching, where a user changes providers digitally in seconds during travel or promotions. Device resale would simplify, as remote profile deletion replaces physical SIM retrieval.
What happens if a user wants to change devices in a slotless era? The process would involve a cloud-based transfer, securely migrating the eSIM profile to the new phone via a quick authentication flow, without needing a tool or physical tray.
What legacy infrastructure still holds physical cards relevant
Legacy infrastructure like corporate fleet management systems and older IoT devices still require physical cards, as their hardware lacks eSIM firmware or secure element support. Many industrial routers, vehicle telematics units, and point-of-sale terminals were built before eSIM standards emerged, making a slot-based card the only way to swap carriers without replacing the entire device. Rural networks also depend on physical SIMs for emergency backup connections, since swapping a card is faster than remote provisioning when towers go down. Why do some modern phones still have a physical SIM slot? For dual-SIM users traveling frequently, a physical card from a local provider remains a reliable fallback if eSIM profiles fail to activate or if roaming rates spike unexpectedly.