Brussels sprout growers are concerned that their vegetable is an "old person's vegetable," that demand is heavily dependent on mature consumers. Last year, consumers $55$ and over bought $$65\mathrm{.}9$ million worth of Brussels sprouts. The population includes $34$ million potential consumers in this category, with $6$ million actually buying Brussels sprouts at least once last year. Overall, the industry sold $$144\mathrm{.}9$ million worth of Brussels sprouts in the United States, where it reckons that there are $187$ million potential customers overall. Calculate category development index for consumers age $55$ and over for the Brussels sprouts industry. Report your answer as a percent. Round to the nearest tenth of a percent. Report $25\mathrm{.}5\%,$ for example, as $"25\mathrm{.}5".$