Management’s Discussion and Analysis of Financial Condition and Results of Operations  (continued) f-8 | 9 Forrester Research | Annual Report 2000 December 31, 1997. The decrease as a percentage of total revenues resulted principally from the larger revenue base in 1998. The increase in expenses was principally due to the addition of direct salespersons and increased sales commission expenses associated with increased revenues. General and Administrative. General and administrative expenses remained constant as a percentage of total revenues at 11% in the years ended December 31, 1998 and December 31, 1997. These expenses increased 49% to $6.7 million in the year ended December 31, 1998 from $4.5 million in the year ended December 31, 1997. The increase in expenses was principally due to staffing increases and costs associated with the opening of our European headquarters. Depreciation and Amortization. Depreciation and amortization expense increased 129% to $2.8 million in the year ended December 31, 1998 from $1.2 million in the year ended December 31, 1997. The increase in this expenses was principally due to investments in our technology infrastructure and costs associated with the opening of our European headquarters. Other Income, Net. Other income, consisting primarily of interest income, increased to $3.0 million in the year ended December 31, 1998 from $2.5 million in the year ended December 31, 1997. This increase was principally due to additional interest income from higher cash and marketable securities balances resulting from positive cash flows from operations. Income Tax Provision. During the year ended December 31, 1998, we recorded a tax provision of  $4.6 million, reflecting an effective tax rate of 37.8%. During the year ended December 31, 1997, we recorded a tax provision of $3.7 million reflecting an effective tax rate of 39.7%. The decrease in effective tax rate resulted primarily from a reduction in our effective state tax rate and an increase in sales through our foreign sales corporation, which we organized in 1998. The following tables set forth a summary of our unaudited quarterly operating results for each of our eight most recently ended fiscal quarters. We have derived this information from our unaudited interim consolidated financial statements, which, in the opinion of our management, have been prepared on a basis consistent with our financial statements contained elsewhere in this annual report and include all adjustments, consisting only of normal recurring adjustments, necessary for a fair presentation in accordance with generally accepted accounting principles when read in conjunction with our consolidated financial statements and related notes included elsewhere in this annual report. Historically, our total revenues, operating profit, and net income in the fourth quarter have reflected the significant positive contribution of revenues attributable to advisory services performed and Forum events held in the fourth quarter. As a result, we have historically experienced a decline in total revenues, operating profit, and net income from the quarter ended December 31 to the quarter ended March 31. Our quarterly operating results are not necessarily indicative of future results of operations. Results of Quarterly Operations