The phrase "a decade has shown" is correct and usable in written English.
It can be used to indicate that over the course of ten years, certain evidence or trends have become apparent.
Example: "A decade has shown that climate change is accelerating at an alarming rate."
Alternatives: "Ten years have demonstrated" or "A decade reveals".
Research like that under way here, where several deer-free plots have been studied for more than a decade, has shown how deer can profoundly change forests.
The track record in Milwaukee, which has had vouchers and a school-choice program for upward of a decade, has shown her no substantial improvement for low-income, nonwhite students.
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But analyses dating back more than a decade have shown that it is not so simple.
Mr. Lee, whose election last December returned conservatives to power after a decade, had shown reservations bordering on disregard for the agreements negotiated by his predecessors.
The past decade has shown a dramatic increase in antibiotic resistance of Enterococcus species, creating an increased need for developing new ways to combat these bacteria.
The past decade has shown us a massively inefficient government that has spent millions in foreign wars, incapacitated by partisan dogma.
She reports that research over the decade has shown some similarities and some differences between male and female business owners.
The past decade has shown that harnessing consumer power to effect positive environmental change is far easier said than done.
Some studies conducted in Northern Europe and North America during the previous decade have shown an inverse socioeconomic trend, as in Scotland for cardiac surgery [ 13] and in England for ophthalmologic surgery and hip replacement [ 14, 15], whilst others have found no or a weak association, as in Canada [ 16], Australia [ 17] and Norway [ 18].
The United Nations is an entity that for decades has shown its antipathy toward Israel, passing numerous one-sided hostile resolutions and, until recently, barring Israel's participation in any regional grouping, excluding it from important committees.
