Gross profit
Gross profit was $5,251,633 for 2023 compared to $4,786,955 for 2022. The increase was primarily attributable to higher revenue. Gross profit as a percentage of revenue (gross margin) was 18.8% and 20.4% for 2023 and 2022, respectively. The lower gross margin in 2023 compared to a year ago was due to increased shipments of lower margin product.
General and administrative expense
General and administrative expense for 2023 and 2022, was $1,771,263 and $1,549,696, respectively, an increase of 14.3%. During 2023 there was an increase in compensation of $138,274, professional services of $44,096 which included higher IT services of $31,588, and additional investment credit reserve of $10,000.
Research and development expense
Research and development expense for 2023 was $501,937, compared to $375,728 for 2022, an increase of 33.6%. This increase was attributed to increases in outside consulting expense of $64,656, compensation of $38,425 and materials and supplies of $12,506. During 2023 the Company initiated sales of certain conductive metal oxides. Specialty materials are being researched for use in niche markets which include custom applications and additive manufacturing. Our development efforts utilize a disciplined innovation approach focused on accelerating time to market for these applications and involve ongoing research and development expense.
Marketing and sales expense
Marketing and sales expense was $484,185 and $381,313, during 2023 and 2022, respectively. This was an increase of $102,872, or 27.0%. During 2023 there was an increase in compensation related to additional staff, and travel expenses of $76,207, and $20,578, respectively. We exhibited at additional international photonics trades shows focused on specific niche markets during 2023.
Stock compensation expense
Included in total expenses were non-cash stock-based compensation costs of $45,485 and $49,321 for 2023 and 2022, respectively. During 2022, the non-employee board members received compensation of 8,755 shares of common stock of the Company with an aggregate value of $29,967 that was recorded as non-cash stock compensation expense in the financial statements. During 2023, non-employee board members received their entire compensation in cash. Compensation expense for all stock-based awards is based on the grant date fair value and recognized over the required service (vesting) period. There was no unrecognized non-cash stock-based compensation expense at December 31, 2023.
Interest
Interest income, net was $286,361 and $19,201 for the years ended December 31, 2023 and 2022, respectively. The increase was primarily due to higher cash and approximately $2.0 million of investments in marketable securities, initially invested in the fourth quarter of 2022, which particularly benefited from an overall increase in interest rates in 2023. Interest expense related to finance lease obligations was $4,309 for 2023 versus $8,600 in 2022.
Income taxes
Income tax expense was $586,710 and $542,395 for the twelve months ended December 31, 2023 and 2022, respectively. The effective tax rate was 21.1% for 2023 compared to 21.7% for 2022. At December 31, 2022, the deferred tax asset was $151,164. As of each reporting date, management considers new evidence, both positive and negative, that could affect its view of the future realization of deferred tax assets. Accordingly, management determined that no valuation allowance was necessary at December 31, 2022. The deferred tax asset was $0, and the deferred tax liability was $69,846 at December 31, 2023.
Net income
Net income for 2023 and 2022 was $2,193,899 and $1,957,024, respectively. Higher revenue and gross profit were partially offset by higher operating expenses and income taxes.