Valuation, valuation, valuation. Investors in European initial public offerings are re-learning an old mantra as shares decline after sales that had high demand before they priced, especially among technology companies.

Rocket Internet AG and online retailer Zalando SE disappointed investors at the start of this month after IPOs that were over-subscribed by several times. Both companies sold shares in Germany in the same week; both sets of shares are now more than 18 percent lower than the IPO price amid unsettled equity markets. They may not be the last to suffer.

“If you look ahead on a European and global level you’ll probably see a bit more volatility in the market,” said Adam Kostyal, head of European listings at Nasdaq OMX Group Inc.

Companies including advertising agency ItaliaonLine SpA, Scottish homebuilder Miller Group Ltd. and French business- services company Spie SA have canceled IPO plans in the last two weeks — all blaming market instability for their decision.

With various global crises including political turmoil in Russia and Ukraine and conflict across the Middle East potentially dissuading other companies from going public, the fourth quarter could end up as a stark contrast to the first nine months of the year.

From January through September 289 companies raised 40.3 billion euros ($51 billion) on European markets, almost four times more than in the same period in 2013, according to a report from PricewaterhouseCoopers LLP. While the consultancy firm projects another 15 billion euros will be raised during the fourth quarter even as risks intensify, that’s barely higher than the 14.8 billion euros raised in the last three months of 2013.

‘Intense Discussion’

“Against a backdrop of global geo-political unrest, volatility has increased at the end of the third quarter,” PwC said in the report, released Thursday.

Investors need to have “an intense discussion” on the right valuations for IPO hopefuls, keeping in mind growth prospects, so they are well received when they trade, Nasdaq OMX’s Kostyal said.

Companies in Europe are feeling the pain more than their American counterparts, in line with broader equity markets. The Bloomberg European IPO Index is down 7.5 percent this year, compared with a 2 percent fall in the Bloomberg IPO Index for the U.S. Having touched recent highs earlier in the year, the U.K.’s benchmark FTSE 100 Index has now fallen 4.7 percent since the start of 2014, while Germany’s DAX is trading 5.7 percent lower and France’s CAC 40 is down 3.6 percent.

“Given the deteriorating economic environment, I would be wary of paying high multiples for new issues,” said Neil Wilkinson, a fund manager for European equities at Royal London Asset Management Ltd.

“The after-market performance of some recent IPOs, such as Rocket Internet, would appear to justify those concerns.”

Still, in Europe’s largest market for IPOs this year -- London -- optimism prevails over the pipeline for this quarter.

“We continue to see healthy investor appetite,” said John Millar, head of primary listings at the London Stock Exchange Group. “As the economy continues to recover and become increasingly global, companies are recognizing the power of a listing.”