No, because this study analyzes historical tax filings, and inheritances are not counted as taxable income.
> big insurance payouts
On average, probably not, because big insurance payouts are (by definition) actuarial anomalies. They're tail-risk events.
I think you might be over-estimating what it takes to be in the top 5%
Here are the numbers -> https://dqydj.com/income-percentile-calculator/
If you earn $170,000, you're in the top 5%. That's absolutely attainable within 5 years of graduating into a high-skill job.
That's also attainable within one's lifetime if they end up doing any sort of management or decision-making (as opposed to just manual labor all their lives).
That said i'm still having a hard time believing the claim that a large number of households will have top 5% earnings. I'd love to see a blog post or something along those lines contexualizing that journal article.
Here are some articles that summarize the primary source:
https://web.archive.org/web/20160327182251/https://taxfounda...
https://www.aei.org/carpe-diem/evidence-shows-significant-in...
Based on the empirical tax analysis, 12% of the population found themselves in the top 1% of the income distribution for at least one year. 39% of Americans spent a year in the top 5% of the income distribution, 56% found themselves in the top 10%, and a whopping 73% spent a year in the top 20% of the income distribution.