Assume you read a text discussing the total value of all IPOs world-wide and those in France, stating France's IPOs' total value is 9% of those world-wide. Is it valid to refer to this percentage as "proportion of IPOs in France"?
I don't think so, though I am not an expert in finance. For me, "the proportion of IPOs in France" may very well refer to the total number of IPOs instead of their total value. I think you need a longer phrase for clarity, such as "the share of France in the total value of IPOs world wide". Perhaps a shorter phrase can be found.
[Edit] What about: "the French share in global IPO value"?