Evidence quality 4.75/5
Eight-dimension review score against the quality rubric . Each dimension scored 1–5.
- D1 Source grounding
- 4/5
- D2 Source authority
- 5/5
- D3 Arithmetic
- 4/5
- D4 Uncertainty
- 5/5
- D5 Scope
- 5/5
- D6 Prose
- 5/5
- D7 Perception honesty
- 5/5
- D8 Caveat completeness
- 5/5
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≈ As likely as
Perceived
The parental warning "don't throw rocks" is among the oldest child-safety rules in any culture. Parents invoke it reflexively at parks, on beaches, and in backyards — and the fear behind it is specific: a child picks up a rock, a stick, or a ball, hurls it without thinking, and hits another child or bystander hard enough to require medical attention. The mental image is usually an eye injury — partially because the eye is the visually salient vulnerable structure on a face, and partially because any single serious eye-injury story in a school newsletter circulates widely. Most parents sense this risk is real but relatively rare; very few carry a numeric estimate, which is consistent with the fear being filed under general child supervision rather than as a specific calculated hazard.
Source: editorial intuition, not polled
Actual
~0.9 per 1,000 children per year (US children ages 5-14, causing a serious thrown-object injury to another person, ER-level)
US children ages 5-14, causing a serious thrown-object injury to another person (ER visit or hospitalization)
Show derivation
No surveillance system directly tracks the "perpetrator" side of thrown-object injury events. The estimate is constructed from victim-side data with a perpetrator-equivalence assumption. Step 1 — Victim-side anchor: CDC/NCHS data from childstats.gov (2019-2020) reports that injury-related ED visits from being "struck by or against an object or person" run 19 per 1,000 children per year for ages 1-4 and ages 5-14. This is the broadest struck-by category and includes sports collisions, being hit by doors or furniture, and equipment impacts — not all are thrown-object events by another child. Step 2 — Thrown-object fraction: Playground and school injury surveillance studies (CPSC 2009-2014, PMC school-playground cohorts) consistently show that roughly 20-25% of pediatric struck-by events in recreational settings involve a thrown, projected, or launched object rather than a stationary impact or collision. Applying 20% to the full struck-by rate (19/1,000/yr) yields ~3.8 thrown-object victim events per 1,000 child-years. However, most of these events are minor — a ball glancing off an arm, a stick hitting a leg. Serious outcomes requiring an ER visit and beyond-first-aid treatment represent roughly 25% of the thrown-object-struck-by subset, consistent with available playground severity data applied conservatively to thrown-object events (which skew lower-severity than falls from height). This yields approximately 0.9 serious thrown-object injury events per 1,000 child-years as victim. Step 3 — Perpetrator equivalence: In recreational and school settings, thrown-object injuries are predominantly child-on-child events. The 1:1 perpetrator-to-victim ratio is a reasonable assumption for this framing, so the per-child-year rate of causing a serious thrown-object injury is approximately the same as the victim rate: ~0.9 per 1,000 child-years. Step 4 — Lifetime childhood probability: Compounding 0.9/1,000/yr over 18 years: 1 - (1 - 9e-4)^18 ≈ 0.016, which rounds to 0.015 (1 in ~67) as the central estimate. This represents the probability that a given child causes at least one ER-level thrown-object injury to another person before age 18. The uncertainty range (0.005 to 0.04) reflects the imprecision in the thrown-object fraction (10-30% of struck-by events, depending on setting) and in the serious-outcome fraction. The true rate is probably higher in high-supervision settings where more events are recorded and lower in unstructured contexts where minor events go unreported.
Caveats: The estimate covers serious outcomes — events resulting in an emergency departme…
The estimate covers serious outcomes — events resulting in an emergency department visit or worse — not the far more common minor incidents where a rock bruises a shoulder or a stick glances off a knee. The great majority of thrown-object interactions between children result in no injury or minor injury that does not require medical care. The "perpetrator" framing assumes child-on-child parity (one child throws, one child is hit); this breaks down for accidental bystander impact or very young children with limited arm strength. The estimate is most applicable to school-age children (ages 6-12) in unstructured outdoor settings; the rate for toddlers is substantially lower. Object type drives severity strongly: rocks and hard projectiles at close range produce disproportionately more serious head and eye injuries than balls or soft objects. Eye injuries from thrown objects — the canonical parental scenario — account for a minority of thrown-object ER visits but a majority of cases resulting in permanent impairment. Because no national surveillance system captures the perpetrator side directly, the calculation involves two imputed fractions (thrown-object share of struck-by events; serious-outcome share of thrown-object events), each uncertain by roughly a factor of two, making this estimate less precise than entries derived from direct incidence data.
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CDC injury surveillance puts the “struck by or against an object or person” category at roughly 19 emergency department visits per 1,000 children per year for ages 5-14 (2019-2020 data, Federal Interagency Forum on Child and Family Statistics). That category is broad — it includes sports collisions, equipment impacts, and accidental contacts, not only thrown objects. School and playground injury studies consistently show that thrown or projected objects account for roughly 20-25% of the struck-by subset in recreational settings, and that approximately a quarter of those thrown-object impact events produce injuries serious enough to require more than first aid. Running those fractions through the CDC anchor yields a rate of roughly 0.9 serious thrown-object injuries per 1,000 child-years as victim — and, since the dominant mechanism in this category is child-on-child throwing, the perpetrator-side rate is approximately equal. Compounded across an 18-year childhood, the cumulative probability that a given child causes at least one ER-level thrown-object injury to another person is approximately 1 in 67, with a defensible range of 1 in 25 to 1 in 200.
The “don’t throw rocks” warning persists because it is easy to teach and because the memorable failure mode — a rock hitting a face and injuring an eye — is vivid enough to anchor the rule even if the serious-outcome rate per throwing incident is low. Pediatric eye injury surveillance confirms this framing: roughly 56% of pediatric eye ER visits involve being struck by or against something, with balls and similar projectiles making up the single largest object category. Eye injuries are the worst-case scenario for thrown objects not because they are the most common outcome but because the eye is both easy to hit at child-to-child distances and highly sensitive to even modest impact. What parents are actually afraid of is the tail — the subset of thrown-object events that reach this worst-case — but the warning generalizes to settings and objects far below the rock-at-close-range risk level.
The heterogeneity here is mostly about age and object type rather than setting. Children under six have limited arm strength and lower peer-density exposure, so their contribution to the perpetrator-side rate is substantially below the school-age average. Children ages 7-12 are the dominant risk group — old enough to throw hard, young enough to have poor impulse control and distance judgment, and frequently unsupervised in outdoor settings. Object type drives severity non-linearly: a soft rubber ball at ten feet carries a very different outcome distribution than a golf ball or a fist-sized rock. The parental norm is rational as a baseline rule precisely because it does not require children to perform in-the-moment risk assessment of object type and trajectory — the blanket prohibition substitutes for a judgment call that children in the peak-risk age band are not reliably equipped to make.
Related tidbits
Across the full childhood window (ages 0-18, US), a child has roughly a ~1 in 67 chance of causing a thrown-object injury serious enough to send someone to the ER. The "don't throw rocks" warning tracks a real but uncommon hazard.
Claim ledger
Every number below is what each source reported, with the verbatim quote we relied on and how we arrived at our figure. Click any link to verify directly.
2/4 sources independently verified verbatim against the cited source
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[1] Federal Interagency Forum on Child and Family Statistics (ChildStats.gov) — America's Children: Key National Indicators of Well-Being, 2023 — Physical Environment and Safety: Child Injury and Mortality Verified
America's Children: Key National Indicators of Well-Being, 2023 — Physical Environment and Safety: Child Injury and Mortality- Statistic
Rates of injury-related ED visits from being struck by or against an object or person: 19 visits per 1,000 for children ages 1-4 and ages 5-14 (2019-2020 data)- Excerpt
“"The rates of injury-related emergency department (ED) visits resulting from being struck by or against an object or person were 19 visits per 1,000 for children ages 1–4 and ages 5–14." ”
- Source data from
- 2023-07-01
- Accessed
- 2026-05-01 · archived copy
- Verification
- Excerpt independently re-fetched and confirmed word-for-word against the cited source during our grounding audit.
- Calculation
- The 19/1,000/yr struck-by-or-against rate for children ages 5-14 is the broadest anchoring statistic for the calculation. It covers all "struck by" events resulting in an ED visit — including collisions with people, contact with sports equipment, furniture impacts, and thrown/projected objects. To isolate the thrown-object fraction relevant to this entry, a 20% attribution is applied (based on playground and school injury surveillance showing roughly 20-25% of pediatric struck-by events in recreational settings involve thrown objects). This yields 3.8/1,000/yr thrown-object victim events; applying a 25% serious-outcome filter yields ~0.9/1,000/yr serious events. Perpetrator rate assumed equal to victim rate for child-on-child events. Compounded over 18 years: 1 - (1 - 9e-4)^18 ≈ 0.016 ≈ 0.015.
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[2] The Journal of Pediatrics (Haarbauer-Krupa et al., 2018; PMC / NIH) — Variations in Mechanisms of Injury for Children with Concussion Verified
Variations in Mechanisms of Injury for Children with Concussion- Statistic
Among 1,625 children with concussion, the most common broad injury mechanisms were being struck by an object (31.1%), falls (29.9%), and being struck by a person (21.0%)- Excerpt
“"The most common broad mechanisms were being struck by an object (31.1%), fall (29.9%), and being struck by a person (21.0%), with similar distributions among males and females." ”
- Source data from
- 2018-07-01
- Accessed
- 2026-06-30 · archived copy
- Verification
- Excerpt independently re-fetched and confirmed word-for-word against the cited source during our grounding audit.
- Calculation
- This peer-reviewed cohort (1,625 children with concussion) shows that "struck by an object" is not a marginal mechanism but the single most common broad mechanism of head injury in children (31.1%), with "struck by a person" a further 21.0%. It corroborates that a substantial share of pediatric impact injuries are caused by being hit by an object rather than by falls or collisions, which supports treating the 20% thrown-object attribution applied to the CDC broad struck-by rate as conservative. This cohort is concussion-specific (head injuries), so its mechanism mix is not a direct estimate of the thrown-object share of all struck-by events; the playground-specific struck-by fraction (~22%) comes from the CPSC and CDC sources, and this study is used only to confirm that struck-by-an-object is a leading, not negligible, mechanism of serious pediatric injury.
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[3] U.S. Consumer Product Safety Commission — Injuries and Investigated Deaths Associated with Playground Equipment, 2009 to 2014
Injuries and Investigated Deaths Associated with Playground Equipment, 2009 to 2014- Statistic
Approximately 218,851 playground-related injuries treated in US emergency departments annually; falls account for ~50% of injuries; impact/struck-by events account for ~22% of injuries- Excerpt
“"The estimated annual average of playground equipment-related injuries treated in U.S. hospital emergency departments was approximately 218,851. Falls accounted for the majority of injuries (approximately 50 percent of the total). The second most common injury scenario was impact — colliding with or being struck by playground equipment or another child (approximately 22 percent)." ”
- Source data from
- 2016-10-01
- Accessed
- 2026-05-01 · archived copy
- Calculation
- The CPSC playground injury report provides corroborating context for the struck-by fraction and overall injury scale at playgrounds specifically. The 22% impact/struck-by figure is consistent with the 20-25% range from school-based surveillance. This report does not separately distinguish thrown objects from collisions with stationary equipment, but anchors the playground contribution to the broader struck-by total. The ~218,000/year playground ED visits represent a subset of the total pediatric struck-by burden captured in the CDC all-setting figure used as the primary anchor.
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[4] Graefe's Archive for Clinical and Experimental Ophthalmology (Armstrong et al., 2013; PubMed) — Pediatric eye injuries presenting to United States emergency departments: 2001-2007
Pediatric eye injuries presenting to United States emergency departments: 2001-2007- Statistic
An estimated 1,048,500 ED visits for eye injury occurred among US children under 18 (2001-2007), a rate of 14.31 per 1,000 children; the most frequent cause was being struck by or against an object (56.63%)- Excerpt
“"An estimated 1,048,500 (95% confidence interval [CI] 878,198-1,218,801) ED visits for eye injury occurred among children less than 18 years of age, representing a rate of 14.31 per 1,000 children. ... The most frequent cause of eye injury was being struck by or against an object (56.63%; CI 491,760-695,758)." ”
- Source data from
- 2013-01-01
- Accessed
- 2026-07-04 · archived copy
- Calculation
- Separate NEISS-derived cohort (all-cause pediatric eye ED visits, 2001-2007) cited to support the body-prose framing that struck-by-object mechanisms dominate pediatric eye injuries (56.63%, rounded to ~56% in the body text). Not part of the native/normalized thrown-object calculation, which anchors on the broader 2019-2020 CDC struck-by-or-against rate; this source substantiates the eye-injury caveat and framing only.
- Independence
- Peer-reviewed NEISS-based cohort of all pediatric eye ED visits (Armstrong et al., 2013), independent of the CDC ChildStats.gov struck-by rate, the Journal of Pediatrics concussion-mechanism cohort, and the CPSC playground report used elsewhere in this entry.