The FTSE 250 has risen by 86% over the last 10 years, compared to a miserly 17% gain for the FTSE 100.

But while the mid-cap index has been a good long-term investment, concerns about the UK economy mean the more UK-focused FTSE 250 has lagged the FTSE 100 by nearly 10% this year.

Despite recent volatility, I think there are still attractive opportunities in the FTSE 250. In today’s article I’ll look at the latest news from three possible contenders.

Rising asset value

Assets under management at Aberdeen Asset Management (LSE: ADN) rose by 2.9% to £301.4bn during the firm’s third quarter, despite net client withdrawals of £8.9bn. The firm reported investment gains of £17.5bn, which equates to a 6% increase in asset value over three months.

Aberdeen’s performance looks pretty respectable to me. Although the group’s shares have now risen by 50% from the five-year lows seen in January, I think there are opportunities for further gains.

I’m attracted to Aberdeen’s diversity, which I believe should leave the group in a good position to deliver medium-term growth.

Dividend cover for the group’s 6.1% yield is likely to be very tight this year. But this situation should improve as earnings start to recover. Now could be a good time to add to a long-term position in Aberdeen shares.

Too late to buy insurance?

Shares in Bermuda-based insurance group Hiscox (LSE: HSX) rose by 2% this morning after the group said that pre-tax profits rose by 52% to £206m in the first half of this year.

However, this gain isn’t quite as impressive as it sounds. Excluding the effect of shifting exchange rates, pre-tax profits actually fell from £150.8m last year to £118.7m during the first half of 2016.

A better measure of performance might be Hiscox’s group combined ratio, which measures the proportion of premiums paid out in claims and costs. This fell from 82.5% to 80.7% this year, suggesting the group has paid out less in claims than during the same period last year.

Although the outlook is improving, Hiscox profits have slipped lower in recent years as a result of soft market conditions. The shares look fully valued to me for now, on 17 times forecast earnings and with an ordinary dividend yield of 2.5%.

Diamond market improving

South African diamond producer Petra Diamonds (LSE: PDL) increased production by 16% to 3.7m carats during the year ending 30 June. This helped to bump up revenue by 1% to $430.9m, despite rough diamond prices falling by 6% last year.

Today’s production and revenue figures are slightly ahead of guidance, which suggests profits should be in line with or ahead of forecasts for adjusted earnings of 9 cents per share.

Petra shares trade on a forecast P/E of 18 for the year just ended, but profits are expected to rise by 115% this year, putting the stock on a forecast P/E of 8.3 for the current year. Management expects to deliver production growth of 25% to 30% this year, as recent capex delivers results.

The outlook seems positive, but Petra shares have risen strongly from November’s low of 52p. I think there may be better value elsewhere in the sector.

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Roland Head has no position in any shares mentioned. The Motley Fool UK has recommended Aberdeen Asset Management. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.