Read the following texts and table with financial data from an S&P 500 earnings report carefully.Based on the question-answer history (if provided), answer the last question. The answer may require mathematical calculation based on the data provided.

Text: supplementary information on oil and gas producing activities ( unaudited ) c o n t i n u e d summary of changes in standardized measure of discounted future net cash flows relating to proved oil and gas reserves ( in millions ) 2006 2005 2004 sales and transfers of oil and gas produced , net of production , transportation and administrative costs $ ( 5312 ) $ ( 3754 ) $ ( 2689 ) net changes in prices and production , transportation and administrative costs related to future production ( 1342 ) 6648 771 . <table class='wikitable'><tr><td>1</td><td>( in millions )</td><td>2006</td><td>2005</td><td>2004</td></tr><tr><td>2</td><td>sales and transfers of oil and gas produced net of production transportation and administrative costs</td><td>$ -5312 ( 5312 )</td><td>$ -3754 ( 3754 )</td><td>$ -2689 ( 2689 )</td></tr><tr><td>3</td><td>net changes in prices and production transportation and administrative costs related to future production</td><td>-1342 ( 1342 )</td><td>6648</td><td>771</td></tr><tr><td>4</td><td>extensions discoveries and improved recovery less related costs</td><td>1290</td><td>700</td><td>1349</td></tr><tr><td>5</td><td>development costs incurred during the period</td><td>1251</td><td>1030</td><td>609</td></tr><tr><td>6</td><td>changes in estimated future development costs</td><td>-527 ( 527 )</td><td>-552 ( 552 )</td><td>-628 ( 628 )</td></tr><tr><td>7</td><td>revisions of previous quantity estimates</td><td>1319</td><td>820</td><td>948</td></tr><tr><td>8</td><td>net changes in purchases and sales of minerals in place</td><td>30</td><td>4557</td><td>33</td></tr><tr><td>9</td><td>accretion of discount</td><td>1882</td><td>1124</td><td>757</td></tr><tr><td>10</td><td>net change in income taxes</td><td>-660 ( 660 )</td><td>-6694 ( 6694 )</td><td>-627 ( 627 )</td></tr><tr><td>11</td><td>timing and other</td><td>-14 ( 14 )</td><td>307</td><td>97</td></tr><tr><td>12</td><td>net change for the year</td><td>-2083 ( 2083 )</td><td>4186</td><td>620</td></tr><tr><td>13</td><td>beginning of year</td><td>10601</td><td>6415</td><td>5795</td></tr><tr><td>14</td><td>end of year</td><td>$ 8518</td><td>$ 10601</td><td>$ 6415</td></tr><tr><td>15</td><td>net change for the year from discontinued operations</td><td>$ -216 ( 216 )</td><td>$ 162</td><td>$ -152 ( 152 )</td></tr></table> .
Question: what was the cash flow balance at the end of 2006?
Answer: 8518.0
Question: what was the balance at the start of the year?

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10601.0
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