Real Madrid's recent Champions League success has shown that squad salary levels are more important than one-off transfer fees, according to new research from KPMG.

The study also suggests that Premier League clubs' recent lack of European can be attributed to owners who don't pass on increased revenues to their squads.

KPMG's Football Benchmark group found that at most of Europe's top clubs, revenues were growing at a much higher rate than salaries -- with the most dramatic rises taking place in the Premier League because of the leap in broadcasting revenues.

The exceptions to this trend for the period between 2011-12 and 2015-16 were Real Madrid, Barcelona, Chelsea and Bayern Munich -- the only clubs to lift the Champions League trophy during this period.

The report on the sustainability of football's business models -- titled "The business of football: Are wages affordable?" -- found that other top clubs across the big five leagues were becoming more profitable, but perhaps at a cost to success on the pitch.

"Between 2011-12 and 2015-16 seasons, all European big-five leagues have grown operating revenues [net of transfer proceeds] in excess of total staff costs," the research said.

"Among these, the broadcasting receipts for the period 2013-2016 sent the English Premier League total operating revenues some 76 percent higher, the most dramatic rise among the leagues under analysis.

"All the Premier League clubs, except Chelsea FC, stay in line with the overall results by aggregate figures; Liverpool FC display the highest growth by both metrics, while Manchester City FC have the most positive result.

"Furthermore, Italian champions Juventus FC and French giants Paris Saint- Germain FC also join this cluster of clubs, as their ability to leverage their revenue streams outperforms the increased remuneration of the staff."

New article: What has been the trend of revenue & staff cost growth in 🇪🇺 big 5 leagues? 📈💰



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💬@andreasartori94 pic.twitter.com/Wlb9rZr1Vz — Football Benchmark (@Football_BM) October 3, 2017

Madrid stand out as an example -- with club president Florentino Perez not having sanctioned a top galactico purchase for over three years, but the club's already star-studded squad still becoming the first to retain the Champions League trophy in the modern era.

Answering questions at Madrid's AGM from club members concerned the club were paying too much to players such as Cristiano Ronaldo and Gareth Bale, Perez said last Monday he was sure that paying top dollar to keep the team's most important players happy was key to long-term success on and off the pitch.

"If we do not renew the contracts of Modric, Kroos et cetera they will go somewhere else," the construction magnate said. "And without those players who won the Champions League we lose sponsors.

"If we did not win the Champions League last year [and have to pay bonuses] we would have almost €100 million in profits. And having won that will bring more income in the future."

As alluded to by Perez, the KPMG research also suggested the lucrative bonuses for winning the UCL in players contracts might actually be an issue for clubs in a financial sense.

"Winning comes at a cost," the study said. "And eventual bonuses or contract renewals awarded might have a stronger impact on a club's books than any success achieved on the international stage."

The research also shows that Premier League club owners are less likely than rivals elsewhere to use higher revenues from broadcasting and other sources to pay their players more.

Although the broadcasting revenues jumped 76 percent from 2013-16, investment in staff costs only increased 56 percent over the same timeframe.