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Performance

· 15 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
79
GRADE
C
FIX
4
REVIEW
3
PASS
6
INFO
2

Performance-focused optimization plan with CWV assessment, top offenders, and time estimates

Mobile Desktop
96
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
91
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
96
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
100
SEO Measures basic SEO optimizations: meta tags, crawlability, link text, and mobile friendliness.

First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.

608 ms

Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.

1.36 s

Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.

4 ms

Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.

0.000

Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.

928 ms

Time to Interactive Time to Interactive — how long until the page is fully interactive and responds to user input. Under 3.8s is good.

2.33 s

Page Load Progression

387 ms
775 ms
1.2 s
1.5 s
1.9 s
2.3 s
2.7 s
3.1 s
Checks
15
6 PASS 3 REVIEW 4 FIX
D
Third-Party Impact
Action
100% third-party, 0 ms blocking
FIX
100% third-party, 0 ms blocking
Warning::
Third-party code accounts for 100% of page weight (1.4 MiB of 1.4 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
D
JS Bundles
Action
16 scripts, 360 KB unused
FIX
16 scripts, 360 KB unused
Warning::
https://www.nber.org/themes/custom/nber/assets/bui...: 147 KB unused (54%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=G-3Y05...: 63 KB unused (41%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-MVR...: 62 KB unused (43%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cdnjs.cloudflare.com/ajax/libs/d3/6.7.0/d3...: 55 KB unused (75%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.nber.org/themes/custom/nber/assets/bui...: 33 KB unused (64%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 360 KB
360 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.nber.org/themes/custom/nber/assets/build/js/libraries-generated.js?tduart273 KB147 KB (54%)✓3rd
https://www.googletagmanager.com/gtag/js?id=G-3Y05NLKEBB&cx=c&gtm=4e64k0h2156 KB63 KB (41%)✓3rd
https://www.googletagmanager.com/gtm.js?id=GTM-MVRPF7C143 KB62 KB (43%)✓3rd
https://cdnjs.cloudflare.com/ajax/libs/d3/6.7.0/d3.min.js73 KB55 KB (75%)✓3rd
https://www.nber.org/themes/custom/nber/assets/build/js/index-generated.js?tduart51 KB33 KB (64%)✓3rd
https://www.nber.org/core/misc/drupal.init.js?v=10.4.91 KB—✓3rd
https://www.nber.org/core/misc/drupal.js?v=10.4.97 KB—✗3rd
https://www.nber.org/modules/contrib/lazy/js/lazy.js?v=10.4.91 KB—✓3rd
https://www.nber.org/core/assets/vendor/once/once.min.js?v=1.0.11 KB—✓3rd
https://www.nber.org/core/misc/drupalSettingsLoader.js?v=10.4.91 KB—✓3rd

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

D
Page Weight Inventory
Action
59 resources · 1.4 MB · 360 KB savings available
FIX
59 resources · 1.4 MB · 360 KB savings available
Warning::
Page weight 410 KB over 1MB target
Got: 1.4 MB Expected: ≤ 1 MB
Info::
~360 KB of savings available
Warning::
58 third-party resources (100% of weight)
Info::
1 resources over 200KB
59 resources · 1.4 MiB · 58 third-party 409.6 KiB over 1MB target
JavaScript 52% · 738.8 KiB
Image 22% · 317.0 KiB
Font 20% · 288.0 KiB
CSS 4% · 55.8 KiB
Document 2% · 31.3 KiB
Other 0% · 2.8 KiB

~359.5 KiB of savings available

Remove unused JavaScript: 359.5 KiB
F
HTTP Caching
Action
No cache headers
FIX
No cache headers
Warning::
No Cache-Control header found
Browsers will use heuristic caching, which can be unpredictable. Set explicit cache headers.

No Cache-Control header

Adding a Cache-Control header can significantly improve repeat-visit performance.

B
Page Weight Budget
1.4 MB transferred, 59 requests
REVIEW
1.4 MB transferred, 59 requests
Info::
Page weighs 3.4 MB (1.4 MB transferred)
Warning::
JavaScript is 739 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 739 KB
Info::
Fonts are 288 KB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 288 KB
Info::
59 HTTP requests
Info::
Estimated 0.29 g CO2 per page load
1.4 MB / 2.4 MB budget
1.4 MB transferred
59 requests
0.29 g CO2 per page load
JavaScript 738.8 KiB 52%
Images 314.3 KiB 22%
Fonts 288.0 KiB 20%
CSS 55.8 KiB 4%
HTML 31.3 KiB 2%
Other 2.9 KiB 0%
Other 1.6 KiB 0%
Other 547 B 0%
Other 450 B 0%
0 2.4 MB 4.9 MB
Under budget

Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.

Why this matters

JavaScript bundle is large — code-split routes and lazy-load off-screen components to defer.

Source: web.dev

Subset fonts to include only used characters, or switch to system font stacks.

Why this matters

Font payload is large — subset to used glyphs only, or fall back to system fonts (zero load time).

Source: web.dev font loading

B
JS Execution Cost
675ms total JS execution
REVIEW
675ms total JS execution
Info::
https://www.nber.org/: 230ms CPU time
Info::
https://cdnjs.cloudflare.com/ajax/libs/d3/6.7.0/d3...: 165ms CPU time
Info::
Unattributable: 78ms CPU time
Info::
https://www.googletagmanager.com/gtm.js?id=GTM-MVR...: 74ms CPU time
Info::
https://www.nber.org/themes/custom/nber/assets/bui...: 66ms CPU time
Warning::
Third-party scripts: 675ms (100% of total)

Main Thread Breakdown

Script Evaluation 35% Other 22% Rendering 17% Style & Layout 14% Script Parsing & Compilation 8%
ScriptTotalScriptingParse/CompileParty
https://www.nber.org/230ms2ms0ms3rd
https://cdnjs.cloudflare.com/ajax/libs/d3/6.7.0/d3.min.js165ms41ms5ms3rd
Unattributable78ms2ms0ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-MVRPF7C74ms63ms10ms3rd
https://www.nber.org/themes/custom/nber/assets/build/js/index-generated.js?tduart66ms59ms4ms3rd
https://www.googletagmanager.com/gtag/js?id=G-3Y05NLKEBB&cx=c&gtm=4e64k0h262ms51ms9ms3rd
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A+
Text Compression
All text resources are compressed
PASS
All text resources are compressed
Info::
All text resources are compressed
All text resources are properly compressed.
A+
Image Optimization
6 images, 0 KB saveable
PASS
6 images, 0 KB saveable
Info::
All images are well-optimized
6 images 314 KB
0 oversized -0 KB
1 legacy format
0 missing dimensions CLS risk
A+
Font Loading
9 fonts (288 KB)
PASS
9 fonts (288 KB)
Info::
9 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

9

288 KB total

Render-blocking

0

of 9

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 500 ms 1.0 s FCP 608 ms LCP 1.4 shttps://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-regular.woff2arimo-v17-latin_greek-r... https://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-regular.woff2 — 16.5 KiB — 34 ms — font-display: swaphttps://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-700.woff2arimo-v17-latin_greek-7... https://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-700.woff2 — 16.4 KiB — 40 ms — font-display: swaphttps://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-italic.woff2arimo-v17-latin_greek-i... https://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-italic.woff2 — 18.2 KiB — 16 ms — font-display: swaphttps://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-700italic.woff2arimo-v17-latin_greek-7... https://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-700italic.woff2 — 18.2 KiB — 13 ms — font-display: swaphttps://www.nber.org/themes/custom/nber/assets/fonts/TiemposHeadlineWeb-Bold.woff2TiemposHeadlineWeb-Bold... https://www.nber.org/themes/custom/nber/assets/fonts/TiemposHeadlineWeb-Bold.woff2 — 40.6 KiB — 18 ms — font-display: swaphttps://www.nber.org/themes/custom/nber/assets/fonts/TiemposHeadlineWeb-Regular.woff2TiemposHeadlineWeb-Regu... https://www.nber.org/themes/custom/nber/assets/fonts/TiemposHeadlineWeb-Regular.woff2 — 41.8 KiB — 14 ms — font-display: swaphttps://www.nber.org/themes/custom/nber/assets/fonts/TiemposHeadlineWeb-Medium.woff2TiemposHeadlineWeb-Medi... https://www.nber.org/themes/custom/nber/assets/fonts/TiemposHeadlineWeb-Medium.woff2 — 40.6 KiB — 21 ms — font-display: swaphttps://www.nber.org/themes/custom/nber/assets/fonts/TiemposHeadlineWeb-Semibold.woff2TiemposHeadlineWeb-Semi... https://www.nber.org/themes/custom/nber/assets/fonts/TiemposHeadlineWeb-Semibold.woff2 — 40.2 KiB — 17 ms — font-display: swaphttps://www.nber.org/themes/custom/nber/assets/fonts/TiemposHeadlineWeb-Regular.woffTiemposHeadlineWeb-Regu... https://www.nber.org/themes/custom/nber/assets/fonts/TiemposHeadlineWeb-Regular.woff — 55.5 KiB — 9 ms — font-display: swap
arimo-v17-latin_greek-r... woff2 swap
Size 16 KB
Load time 34 ms
Start 284 ms
Risk FOUT — text flashes from fallback to web font
arimo-v17-latin_greek-7... woff2 swap
Size 16 KB
Load time 40 ms
Start 285 ms
Risk FOUT — text flashes from fallback to web font
arimo-v17-latin_greek-i... woff2 swap
Size 18 KB
Load time 16 ms
Start 308 ms
Risk FOUT — text flashes from fallback to web font
arimo-v17-latin_greek-7... woff2 swap
Size 18 KB
Load time 13 ms
Start 308 ms
Risk FOUT — text flashes from fallback to web font
TiemposHeadlineWeb-Bold... woff2 swap
Size 41 KB
Load time 18 ms
Start 308 ms
Risk FOUT — text flashes from fallback to web font
TiemposHeadlineWeb-Regu... woff2 swap
Size 42 KB
Load time 14 ms
Start 308 ms
Risk FOUT — text flashes from fallback to web font
TiemposHeadlineWeb-Medi... woff2 swap
Size 41 KB
Load time 21 ms
Start 308 ms
Risk FOUT — text flashes from fallback to web font
TiemposHeadlineWeb-Semi... woff2 swap
Size 40 KB
Load time 17 ms
Start 412 ms
Risk FOUT — text flashes from fallback to web font
TiemposHeadlineWeb-Regu... woff swap
Size 55 KB
Load time 9 ms
Start 413 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
Optimization checklist
  • Preload critical fonts (priority=high)
  • Use woff2 format for all fonts
  • Set font-display to swap, optional, or fallback
  • Subset large fonts (≤100 KB each)

Fixing the unchecked items could save ~17 KB and ~34 ms

A+
Resource Caching
All resources properly cached
PASS
All resources properly cached
Info::
No caching issues found
All static resources have appropriate caching headers.
A+
Critical Rendering Path
No render-blocking resources
PASS
No render-blocking resources
Info::
No render-blocking resources detected
A+
Resource Hints
No optimization needed
PASS
No optimization needed
Info::
No resource hint issues
Network Waterfall
59 requests over 1007ms
INFO
0 ms 500 ms 1.0 s FCP 608 ms LCP 1.4 shttps://nber.org// https://nber.org/ — 301 — 204 B — 7 ms — h2https://www.nber.org/www.nber.org/ https://www.nber.org/ — 200 — 31.3 KiB — 271 ms — h2https://www.nber.org/modules/custom/nber_user_auth/js/cookies.js?tduartwww.nber.org/modules/custom/nber_us... https://www.nber.org/modules/custom/nber_user_auth/js/cookies.js?tduart — 200 — 1.2 KiB — 29 ms — h2https://www.nber.org/sites/default/files/google_tag/primary/google_tag.script.js?tduartwww.nber.org/sites/default/files/go... https://www.nber.org/sites/default/files/google_tag/primary/google_tag.script.js?tduart — 200 — 579 B — 44 ms — h2https://www.nber.org/core/modules/system/css/components/align.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/align.module.css?tduart — 200 — 581 B — 14 ms — h2https://www.nber.org/core/modules/system/css/components/fieldgroup.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/fieldgroup.module.css?tduart — 200 — 374 B — 20 ms — h2https://www.nber.org/core/modules/system/css/components/container-inline.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/container-inline.module.css?tduart — 200 — 439 B — 16 ms — h2https://www.nber.org/core/modules/system/css/components/clearfix.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/clearfix.module.css?tduart — 200 — 578 B — 17 ms — h2https://www.nber.org/core/modules/system/css/components/details.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/details.module.css?tduart — 200 — 321 B — 16 ms — h2https://www.nber.org/core/modules/system/css/components/hidden.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/hidden.module.css?tduart — 200 — 937 B — 14 ms — h2https://www.nber.org/core/modules/system/css/components/item-list.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/item-list.module.css?tduart — 200 — 513 B — 29 ms — h2https://www.nber.org/core/modules/system/css/components/js.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/js.module.css?tduart — 200 — 591 B — 17 ms — h2https://www.nber.org/core/modules/system/css/components/nowrap.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/nowrap.module.css?tduart — 200 — 389 B — 34 ms — h2https://www.nber.org/core/modules/system/css/components/position-container.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/position-container.module.css?tduart — 200 — 401 B — 39 ms — h2https://www.nber.org/core/modules/system/css/components/reset-appearance.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/reset-appearance.module.css?tduart — 200 — 542 B — 19 ms — h2https://www.nber.org/core/modules/system/css/components/resize.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/resize.module.css?tduart — 200 — 376 B — 24 ms — h2https://www.nber.org/core/modules/system/css/components/system-status-counter.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/system-status-counter.css?tduart — 200 — 561 B — 29 ms — h2https://www.nber.org/core/modules/system/css/components/system-status-report-counters.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/system-status-report-counters.css?tduart — 200 — 611 B — 27 ms — h2https://www.nber.org/core/modules/system/css/components/system-status-report-general-info.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/system-status-report-general-info.css?tduart — 200 — 435 B — 29 ms — h2https://www.nber.org/core/modules/system/css/components/tablesort.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/tablesort.module.css?tduart — 200 — 517 B — 39 ms — h2https://www.nber.org/core/modules/views/css/views.module.css?tduartwww.nber.org/core/modules/views/css... https://www.nber.org/core/modules/views/css/views.module.css?tduart — 200 — 492 B — 17 ms — h2https://www.nber.org/modules/custom/nber_charts/css/unemployment-graphic.css?tduartwww.nber.org/modules/custom/nber_ch... https://www.nber.org/modules/custom/nber_charts/css/unemployment-graphic.css?tduart — 200 — 549 B — 31 ms — h2https://www.nber.org/modules/contrib/paragraphs/css/paragraphs.unpublished.css?tduartwww.nber.org/modules/contrib/paragr... https://www.nber.org/modules/contrib/paragraphs/css/paragraphs.unpublished.css?tduart — 200 — 362 B — 36 ms — h2https://www.nber.org/modules/contrib/sitewide_alert/css/sitewide_alert.css?tduartwww.nber.org/modules/contrib/sitewi... https://www.nber.org/modules/contrib/sitewide_alert/css/sitewide_alert.css?tduart — 200 — 476 B — 22 ms — h2https://www.nber.org/themes/custom/nber/assets/build/css/nber-generated.css?tduartwww.nber.org/themes/custom/nber/ass... https://www.nber.org/themes/custom/nber/assets/build/css/nber-generated.css?tduart — 200 — 46.0 KiB — 47 ms — h2https://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-regular.woff2www.nber.org/themes/custom/nber/ass... https://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-regular.woff2 — 200 — 16.5 KiB — 34 ms — h2https://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-700.woff2www.nber.org/themes/custom/nber/ass... https://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-700.woff2 — 200 — 16.4 KiB — 40 ms — h2https://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-italic.woff2www.nber.org/themes/custom/nber/ass... https://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-italic.woff2 — 200 — 18.2 KiB — 16 ms — h2https://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-700italic.woff2www.nber.org/themes/custom/nber/ass... https://www.nber.org/themes/custom/nber/assets/fonts/arimo-v17-latin_greek-700italic.woff2 — 200 — 18.2 KiB — 13 ms — h2https://www.nber.org/themes/custom/nber/assets/fonts/TiemposHeadlineWeb-Bold.woff2www.nber.org/themes/custom/nber/ass... https://www.nber.org/themes/custom/nber/assets/fonts/TiemposHeadlineWeb-Bold.woff2 — 200 — 40.6 KiB — 18 ms — h2
0 ms 500 ms 1.0 s FCP 608 ms LCP 1.4 shttps://nber.org// https://nber.org/ — 301 — 204 B — 7 ms — h2https://www.nber.org/www.nber.org/ https://www.nber.org/ — 200 — 31.3 KiB — 271 ms — h2https://www.nber.org/modules/custom/nber_user_auth/js/cookies.js?tduartwww.nber.org/modules/custom/nber_us... https://www.nber.org/modules/custom/nber_user_auth/js/cookies.js?tduart — 200 — 1.2 KiB — 29 ms — h2https://www.nber.org/sites/default/files/google_tag/primary/google_tag.script.js?tduartwww.nber.org/sites/default/files/go... https://www.nber.org/sites/default/files/google_tag/primary/google_tag.script.js?tduart — 200 — 579 B — 44 ms — h2https://www.nber.org/core/modules/system/css/components/align.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/align.module.css?tduart — 200 — 581 B — 14 ms — h2https://www.nber.org/core/modules/system/css/components/fieldgroup.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/fieldgroup.module.css?tduart — 200 — 374 B — 20 ms — h2https://www.nber.org/core/modules/system/css/components/container-inline.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/container-inline.module.css?tduart — 200 — 439 B — 16 ms — h2https://www.nber.org/core/modules/system/css/components/clearfix.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/clearfix.module.css?tduart — 200 — 578 B — 17 ms — h2https://www.nber.org/core/modules/system/css/components/details.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/details.module.css?tduart — 200 — 321 B — 16 ms — h2https://www.nber.org/core/modules/system/css/components/hidden.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/hidden.module.css?tduart — 200 — 937 B — 14 ms — h2https://www.nber.org/core/modules/system/css/components/item-list.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/item-list.module.css?tduart — 200 — 513 B — 29 ms — h2https://www.nber.org/core/modules/system/css/components/js.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/js.module.css?tduart — 200 — 591 B — 17 ms — h2https://www.nber.org/core/modules/system/css/components/nowrap.module.css?tduartwww.nber.org/core/modules/system/cs... https://www.nber.org/core/modules/system/css/components/nowrap.module.css?tduart — 200 — 389 B — 34 ms — h2https://www.nber.org/core/modules/system/css/components/position-container.module.css?tduartwww.nber.org/core/modules/system/cs... 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HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
100% of JavaScript execution is third-party
First-party Third-party 675ms · 455KB · $9/mo
www.nber.org
Other
Costly
Execution 230ms
Transfer 31 KB
Monthly Cost $3/mo
cdnjs
CDN
Optional
Execution 165ms
Transfer 73 KB
Unused 75%
Monthly Cost $2/mo
Unattributable
Other
Optional
Execution 78ms
Transfer 0 KB
Monthly Cost $1/mo
Google Tag Manager
Tag Manager
Optional
Execution 74ms
Transfer 143 KB
Unused 43%
Monthly Cost $1/mo
www.nber.org
Other
Optional
Execution 66ms
Transfer 51 KB
Unused 64%
Monthly Cost $1/mo
Google Tag Manager
Tag Manager
Optional
Execution 62ms
Transfer 156 KB
Unused 41%
Monthly Cost $1/mo

These scripts may cost more than they're worth

  • www.nber.org adds 230ms and costs ~$3/month

100% of JavaScript execution time is spent on third-party scripts. Consider auditing which scripts are essential.

Why this matters

When third-party JS execution time exceeds your own, performance gains from frontend work are capped by code you don't own.

Learn more ▾

Every millisecond of third-party JS competes with your own for main-thread time. If their share is bigger than yours, optimization on your code base barely moves the needle. Audit, defer, or remove third-parties before further frontend optimization. Use Lighthouse's third-party audit to identify the worst offenders.

Source: web.dev

www.nber.org takes 230ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

75% of cdnjs's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

Source: web.dev

64% of www.nber.org's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

Source: web.dev

How third-party costs are calculated

All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.

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