Exchange-traded funds tracking the financial sector were among the worst performers of a down week following dreary earnings reports from several brokers.

For the week, the Ultra Financial ProShares ( UYG) ETF slumped 14.4% to $31.26. The iShares Dow Jones U.S. Broker-Dealers ( IAI) ETF was lower by 8.4% to $43.24. The Financial Select Sector SPDR ( XLF) ETF lost 7.3% to $27.46.

The group was a drag on the market for much of the week. On Tuesday, Citigroup ( C) posted a greater-than-expected quarterly loss that came after the company recorded a pretax writedown of $18.1 billion because of the mortgage mess.

The following day, JPMorgan ( JPM) said its fourth-quarter profit fell 34% from a year ago amid a $1.3 billion writedown tied to subprime mortgage losses. Then on Thursday, Merrill Lynch ( MER) reported a fourth-quarter loss of almost $10 billion and a writedown $14.6 billion.

Insurers also suffered a costly week. Bond insurers MBIA ( MBI) and Ambac ( ABK) lost significant ground as ratings agencies zeroed in on their triple-A ratings.

AIG ( AIG), Allianz SE ( AZ), and AXA ( AXA) also finished lower for the week due to fears of the subprime crisis crippling counterparty insurers.

The iShares Dow Jones U.S. Insurance ( IAK) ETF dropped 9% to $43.95. The KBW Insurance ( KIE) ETF lost 8.3% to $47.06. The PowerShares Dynamic Insurance ( PIC) ETF fell 6.8% to $15.52.

Energy-related ETFs also fell for the week as crude finished with a 2.3% decline over the five sessions at $90.57. Among individual names, Exxon Mobil ( XOM), ConocoPhillips ( COP), Valero ( VLO), Halliburton ( HAL) and Transocean ( RIG) finished the week in the red.

The iPath S&P GSCI Crude Oil Index ( OIL) shed 2.6% to $52.68. The PowerShares DB Oil ( DBO) lost 2.5% to $32.65. The United States Oil ( USO) declined 2.5% to $71.27.

Surprisingly, homebuilders were among few winners for the week, as D.R. Horton ( DHI), Hovnanian ( HOV), Toll Brothers ( TOL) and Pulte Homes ( PHM) rose.

The SPDR S&P Homebuilders ( XHB) ETF added 2.9% to $17.14. The iShares Dow Jones U.S. Home Construction ( ITB) ETF tacked on 2.6% to $14.83.