The phrase "have created since" is grammatically correct and can be used in written English.
It is typically used when talking about something that has come into existence over a period of time. For example, "We have created several new products since the launch of the company."
Dr David Lowry Stoneleigh, Surrey Gordon Brown's "British jobs for British workers" can only mean that the half a million jobs he claims to have created since Labour came to power were not for British workers.
The crisis in Syria, the unrest that became a civil war that became a nightmare, created, as all wars have created since human beings started living in villages, refugees.
"Cyril fits the criteria we set out… He is a key part of our long-term development and will help us build the foundations we have created since we first entered the sport in September 2009".
In Chapter 2, "Are We Stuck?", Zuk argues against the idea that agriculture is the worst thing that ever happened to us, invoking Spencer Wells' notion that every major disease affecting modern human populations "has its roots in the mismatch between our biology and the world we have created since the advent of agriculture" (p. 46).
The new committee is the second special panel Republicans have created since they won the House majority in 2011.
From the painted sail shapes edition I produced in preparation for this residency, to the following works I have created since arriving.
"The positive spirit that Didier Deschamps has created since he took over has really helped.
But that's precisely what Eric Kayser has created since he opened his little boulangerie on Rue Monge near the Sorbonne in Paris in 1996.
Mythology, conflict and transformation are recurring elements in the distinctive body of work the Seattle composer Garrett Fisher has created since founding his performance troupe, the Fisher Ensemble, in 1995.
Then comes one of the most animally thrilling episodes that any composer has created since Ligeti was at the height of his powers.
As chairman and chief executive of the Manhattan advertising agency Korey Kay & Partners, Mr. Kay has written about half of more than 80 slogans that the company has created since its founding in 1982.
